Valentina Lisitsa, an ethnic Russian born in Ukraine who now lives in the United States, said in a Facebook post that she has been accused of "inciting hatred" on Twitter because of her comments on the conflict in Ukraine.
While it's not uncommon for workers to be penalized for expressing opinions on social media that reflect poorly on their employer, it's difficult to make that case for Lisitsa, said Cara Zwibel of the Canadian Civil Liberties Association.
"It's hard to see the connection between what she said and what the duties of her job are and how it would affect it," Zwibel said.
"If the idea is just that the orchestra wants to avoid controversy, I don't find that a particularly compelling reason. The fact that maybe there would be some people protesting is, again, not a reason to let her go." she said.
"I think there is a problem with the message that this sends to artists that they may have trouble getting jobs or keeping jobs if they express views that are unpopular or controversial."
In her post, Lisitsa said she has been speaking out against the "atrocities" of the civil war, particularly those committed against the Russian minority in Ukraine's eastern and southern regions.
She said she has been "watching helplessly" as her country slides "ever faster into the abyss" and had taken to Twitter "to get the other side of the story heard."
In an interview with RT News, a Russian television network, Lisitsa noted that she always separated music from politics.
"Partially I think it was my mistake in a way, because now my tweets have caught up with me," she told the media outlet.
"I'm totally for freedom of speech, for freedom of discussion, of argument, of heated argument. That's what I've been doing on Twitter, delivering the other point of views. But what I didn't expect that would ever happen is that my music would be silenced."
TSO president and CEO Jeff Melanson said Lisitsa was replaced due to comments she made on social media.
"This is not about free speech, this is not about a political perspective or persuasion, this is about very offensive, intolerant comments about people," Melanson said Tuesday night.
Melanson said the TSO compiled seven pages of tweets after getting complaints from "hundreds" of people and received clarification last week that they were Lisitsa's tweets.
"This is a very extreme example of intolerant and offensive speech ... I've never seen anything like it," he said.
Lisitsa has promised to perform a free concert in Toronto for her fans and supporters, but tweeted Monday night that she thought she'd found a venue for the free concert but they backed out after being "threatened."
The TSO said in a release Tuesday night that Rachmaninoff's Piano Concerto No. 2 had been removed from the program for Wednesday and Thursday and both performances would focus entirely on Mahler's Fifth Symphony.
The TSO earlier said performance would proceed with Toronto pianist Stewart Goodyear replacing Lisitsa.
However, in a statement apparently posted by Goodyear on his Facebook fan page Tuesday, he said he was "bullied into declining this engagement."
He said he found himself "in the middle of a social media frenzy" with words of "bile and hatred" hurled at him from all sides. Goodyear said he was accused of supporting censorship and what began as one of the happiest moments of his life turned into a "shattering display of mob hysteria."
Goodyear said being asked to perform Rachmaninoff's 2nd Piano Concerto in Toronto with the orchestra was a dream come true.
"Yesterday, my dream was shattered," he wrote.
"With all due respect to the pianist who I was going to replace ... one must own one's opinions and words, and have the courage to defend her position without hiding behind the pseudonym, "NedoUkarinka."
"Free speech has consequences, and one most own one's position," added Goodyear. "Dragging other people who have nothing to do with her position does nothing constructive.
Ticketholders for both performances will receive a complimentary ticket to an upcoming performance while those who choose not to attend the concerts can request a refund.
Taras Zalusky, executive director of the Ukrainian Canadian Congress, says his group, which represents approximately 1.3 million Ukrainians in Canada, supports the orchestra's move.
"To have done otherwise would have been a tacit endorsement of her hateful comments," Zalusky said, calling Lisitsa a "Putin troll."
Lisitsa has used Russian derogatory terms to refer to Ukrainians on her Twitter feed, he said.
"I think if you were to just substitute any other group for Ukrainian in her posts I think it would be very apparent to anyone ... the hate speech and venom that she is spewing," Zalusky said.
The controversy sparked a public debate online, with many, including the Russian embassy in Canada, defending Lisitsa's right to free speech while others hailed the orchestra's decision.
"Witch-hunting US Senator McCarthy would applaud. Stop character assassination," said one of the embassy tweets in a reference to late U.S. senator Joseph McCarthy, who exploited the fear of communism in the 1950s to attack various groups, often representing hearsay as fact.
"The decision to cancel @ValLisitsa's concert in Toronto is a black stain upon the @TorontoSymphony and Canada. #LetValentinaPlay," another person wrote.
"Good job TorontoSymphony! Ban those hate and propaganda spreaders," read another message.
Lisitsa performed in Niagara-on-the-Lake, Ont., on Saturday and organizers said they were saddened by the controversy.
Christine Mori, founder and artistic director for Bravo Niagara!, said she was aware of Lisitsa's tweets before booking the concert, but didn't feel it warranted intervention.
"I knew that there might be some backlash because of her political statements that she was making, but we did not get involved in that and I do believe in freedom of speech," she said Tuesday.
"She did not speak politically at all at the concert...and we presented her as Valentina the pianist."
Mori said she hoped Lisitsa's other Canadian performances would still go ahead. The pianist is scheduled to perform in Calgary on June 5 and 6.
Canada has imposed sanctions against Russia over its annexation of Crimea in March 2014, and has repeatedly urged Russian President Vladimir Putin to stop supporting rebels fighting government troops in eastern Ukraine.
Prime Minister Stephen Harper has travelled to Kyiv to show his support and Canada has provided non-lethal military equipment to the Ukrainian government and humanitarian support and assistance to civilian population.