Before word of Salesforce’s planned acquisition of Slack leaked last week, investor sentiment about the workplace chat provider had decidedly soured, causing its stock to lose about a quarter of its value since Slack went public in June of last year. A big reason was competition from Microsoft, that old bogeyman for any upstart in the market for productivity applications.

But Slack CEO Stewart Butterfield, in an interview on Wednesday evening with The Information, bristled at the notion that Microsoft can squash Slack with Teams, its workplace collaboration product, by leveraging its vast sales and marketing muscle. “It almost seems sometimes like it’s a matter of faith for people,” Butterfield said. “It’s not based on any empirical evidence—it’s just people think Microsoft is a bigger company, and they have a huge channel, and so they’ll inevitably win, despite the fact that we win.”