Eric Revie of Glad Tidings Community Church says he was there with his wife and two children when he asked the manager to tell the couple to tone it down.
Riley Duckworth, 25, of London, and her partner Patricia Pattenden, 23, say they were told to leave the coffee shop because they are lesbians.
But Revie says at the time he thought it was a man and woman and found out the couple was actually same sex after he complained.
A spokeswoman for Tim Hortons says the couple was asked to leave after they "went beyond public displays of affection" while visiting the coffee shop three weeks ago.
Duckworth says she and Pattenden were outside drinking coffee with a group of family and friends and kissed once or twice but denies they were groping each other.
"There was a couple that were straddling each other, making out... not just kissing, going further than that," Revie told CFCO radio in Chatham on Monday.
"I had my children there, I asked the manager if she could ask them to tone it down," he said.
Duckworth said she and Pattenden were told "to leave within five minutes or the cops would be called."
"The manager said that our behaviour was inappropriate and that it was a family friendly establishment and it wasn't acceptable there," Duckworth said.
They were shocked but left to avoid creating a scene, she said. They have been to the same outlet previously and had received stares from customers, but nothing had ever been said, she added.
A Facebook group was created Sunday evening calling for a demonstration outside the coffee shop on Thursday that will be attended by friends, family and supporters including members of Pride Chatham-Kent.
By Monday afternoon, several hundred people had joined the Facebook group.
Revie said he had no idea the couple he was complaining about was gay.
"At the time that I went to talk to the manager, I was under the impression that it was a guy and girl, not two girls," Revie said.
Alexandra Cygal, manager of public affairs at Tim Hortons' head office, said it was not the store's intention to "offend or target anyone based on their sexual orientation."
"Tim Hortons and its restaurant owners have always welcomed all families and communities to their restaurants and will continue to do so," she said.
"The guests' behaviour went beyond public displays of affection and was making other guests feel uncomfortable," she said.
The management has apologized to the women and invited them back to their restaurant, added Cygal.
Duckworth said she was not contacted directly by anyone at Tim Hortons and read the apology for the first time on a website.
Duckworth said she'll never return to Tim Hortons again.
"We want to make sure this won't happen again to anybody else because it's wrong and it should have never happened in the first place."