Questions about issues such as race and sexuality often attract some less-than-polite comments, and so moderators tend to be quite proactive about pruning comments on such questions. The last thing this site needs is an ugly fight in comments about hot-button issues. Even the questions themselves can be controversial, let alone the comment sections.
Your comment wasn't especially bad, but it certainly wasn't constructive or particularly relevant to the question at hand. It also might be taken as offensive by some (for example, those who frequent transgender forums), so I thought it best to remove the comment before it could lead to a lengthier discussion. Don't take this as a reprimand or anything: comments are transitory by design, and they're being deleted all the time for a variety of reasons, usually nothing to do with offensiveness.
As for why your comment was deleted so fast, that's because
mods are omnipresent I just happened to load the page and read that question and its comments about 1 minute after you commented :-)