That’s all it is: somebody’s hate towards someone else for no other reason than their sexual orientation. The "defense" gay panic (and trans, don’t forget that) is an excuse for, as another user said, hate crimes--and sometimes even murder. How in the world do some people think this is okay?
Receiving an unwanted homosexual advance is just the same as receiving an advance from anyone you don't find sexually attractive. Supposing you are a male who only likes brunette females, could you use a 'blonde panic' defense if you killed a blonde woman who came onto you? Further, supposing this was a legitimate defense; if homosexual advances panic or anger someone to the extent that they have a psychotic episode, hadn't they ought to be sectioned for the safety of others, anyway?
Unfortunately there may be homosexuals out there that may provoke people on purpose and they end getting hurt or worse when they should not have provoke people in the first place and so they should not abolish the gay panic defense because people should have the right to self defense if they are being stalked by a gay.