How do you define what's a fireable homophopic offense. You need to discuss it, you can't shut it down because its political and uncomfortable to discuss. You need to listen to the people that are being made uncomfortable and have these discussions. "stop being political" is making a decision, it's the side of no change.

If you see a homophobic (or racist, or sexist, or inappropriate, etc) offense, you should absolutely report it to your superior and/or HR, and AFAICT Basecamp's changes don't say you shouldn't. It sounds like they're just banning discussions in the open channels with coworkers ("Hey everyone, do you think what Bob did was homophobic?").

Of course, I might be misinformed on 1) whether you're still allowed to report workplace offenses to HR, and/or 2) whether company-wide conversation about your coworkers' potential offenses is actually a positive thing to allow.