You do sound quite resentful of this man achieving a senior position to you when you have worked there for longer.
Even if you want to leave, don't go about it this way. You never know when you might want to return, or if your paths will cross with someone from this company in the future and they remember your behaviour?
There's nothing clever about behaving badly to get the sack. I know, I have a colleague doing a similar thing at the moment and she's so blinkered to her own issues that she doesn't care how much trouble she's causing to everyone else.
Without going into too much detail, our boss has two close relatives undergoing cancer treatment, one responding well, the other too early to say yet what might happen to them. They also have a friend of over 25 years dying from cancer, and an employee who has just been diagnosed with it.
They are obviously under a lot of stress because of this, yet this colleague hasn't considered any of that. Nor has she considered the impact that she's had on other colleagues, not just at work but with repercussions at home as well, as the extra demands her laziness is putting on everyone else impacts on our lives at home.
And all because she is trying to get the sack. Yet she has also threatened to sue the company if she does lose her job.
She's a thoroughly unpleasant and nasty person.
Do you really want that reputation to be yours?
Perhaps this man was trying to help you when he offered you the working lunch. Perhaps he's noticed that you are letting things slide and he wants to help you before you lose your job. Perhaps he was hoping to find out what's making you behave as you are so he can do something about it.
And yes, straight ally supporting LGBT rights is a normal and widely used statement. There's nothing wrong with him using that in his email signature and so it does seem as though your personal animosity towards him is just looking for trouble where there is none.