I think the problem here is that comments like that do nothing but stifle conversation. There is a strong negative psycholinguistic association with terms like "racist", "sexist" and "homophobic". The reason for this is that most people (white power advocates and the like being exceptions) take great exception to being called these things, and in many cases people's careers have been ruined due to casual remarks like that. Still not as bad as McCarthy Era society where you could be blacklisted for being called a "pinko" (a communist sympathizer, so you are just a little red), but the concern there is real.
So addressing points that you want to view as "homophobic" or "sexist", I would suggest rather than just immediately paint the opponent as a deviant (a logical fallacy called Ad Hominem), you should state "Your statement X is wrong because of the following inconsistencies, contrary facts, statistics, etc.". The key to a well established debate or dialectic is to address points made, and the logical premises and conclusion of said points. This leads to (hopefully) a broader understanding of the matter by both parties involved, and often helps uncover truth when it sometimes can be blurry around the edges.
Unless all you care about is winning in the public eye, in which case I would encourage to keep arguing like modern politicians and forget that example below used to be the common form of pundit debate...
Edit: Vidal did spend a little too much time calling Buckley a "crypto-nazi" during that debate, but otherwise an incredible exchange of ideas.