So what pisses you off more; the fact you think he's gay, or that he's having explicit conversations over FB that have led to meetings in the park?

Advice you asked for so here it is....

Do NOT condemn your kid for supposedly being "gay." That alone will start WWIII in the mind of a 15 yr old and could possibly make him feel unaccepted by you. We ALL know what can happen when teens feel this way!

IF you feel the need to snoop on your kid's FB conversations, you must feel he needs to be gawked upon. If this is the case, and he is untrustworthy, remove his computer after you approach him with your VALID reason for not trusting him.

If you can deal with your son's sexuality, great. Let him come to you, instead of you emotionally beating him down for it without even intending to do so. If you can't deal with it, you may lose him in many ways. One being he will hate you for your judgment instead of support. Worse would be what we all know can happen when teens feel unaccepted by their parents and peers...hint hint.