With only days left before a scheduled summer recess and an autumn election call that will end this Parliament, tempers appear to be growing short.
During question period, McCallum asked about Conservative plans to introduce legislation to ban face coverings at citizenship ceremonies.
He accused Alexander of assuming all Muslim women who wear the veil are "terrorists, unless proven otherwise," and demanded that the minister apologize.
Alexander hotly denied saying any such thing and invited McCallum to repeat it outside the Commons, where he would have no protection against a libel suit.
He then urged McCallum to apologize for "decades of racism," reaching all the way back to the era of Mackenzie King and accusing the Liberals of keeping people from South Asia, East Asia and the Caribbean out of Canada.
McCallum started it off with this remark:
"The minister of citizenship and immigration assumes all Muslim women who wear the veil are terrorists, unless proven otherwise," he said. "This is simply unacceptable, so will he apologize to all Muslim Canadians?"
Alexander's entreaties to step outside, in parliamentary terms, did little to stem McCallum's attack.
He noted that 2013 police figures showed a drop in overall reporting of hate crimes, but a rise in hate crimes directed at Muslims. He blamed the government.
"It is obvious from the minister's previous statement that he equates terrorism with niqabs," McCallum said. "When only Muslims face a rise in hate crimes, it is obvious the government's toxic anti-Muslim rhetoric is a part of the problem."
The comments were "most outrageous untruths I have yet to hear in this place," Alexander shot back.
"I would invite that member to apologize for decades of racism by his party under Mackenzie King, blocking South Asians from coming to this country, blocking East Asians from coming to this country, blocking Caribbeans from coming to this country.
"The injustice of backlogs under the Trudeau regime and the Chretien era, it is that party that has been the racist party in this Parliament over decades."
New Democrat Peggy Nash, the next MP in the question period lineup, was briefly taken aback.
"Whoa," Nash said.