I think the way your original thread got derailed was unfortunate. I don’t think you were saying that because he’s now come out as bi, being bi will make him unfaithful. But I do think you’re reacting to the fact that he’s chosen to do this so publicly when - if he isn’t planning on exploring that side of his sexuality - there is little need to do so. And I can see why that would make you uneasy.
It may be that all is as he says and he has no intention of acting on it. That’s the best case scenario, and as others have said, being bi doesn’t automatically mean you cheat on people. Lots of bi people are monogamous.
Or it may be that by coming out so openly he is hoping to soften you up down the line for some discussion about opening the marriage so he can sleep with men, and by enlisting the support of others in his coming out he hopes they’ll help talk you round or make you feel unreasonable for refusing to let him do so.
It may be that he’s already been exploring and this is a pre-emptive strike.
In every case, though, this is bound to be a massive shock. It’s one thing to love your husband and want to be supportive, especially when they’re getting praise for being brave and honest in coming out from those whose lives have not just been shaken to the core, it’s another to be able to smile sweetly and validate them when you’re bound to have questions and fears and anger at the lies and the way he came out to your kids before you. You’re allowed to feel angry. You’re allowed to feel manipulated. And you’re allowed to ask questions and not just wave rainbow flags and kill the fatted calf.
Have you asked him why he now feels the need to come out so publicly if he’s committed to your marriage and will therefore not be sleeping with men? Because the answer to this is so important. And how he answers - with evasion, confidence, reassurance, however - is something you need to watch very carefully.
If he loves you, if he’s committed to your marriage, he should also be capable of sufficient empathy to understand how disruptive his coming out is for you, and that he’s pulled the rug out from under you. He should be trying to reassure you that nothing is going to change, and telling you he loves you.
So how is he behaving? Is this all the “new fabulous DH show” with him centring himself and his feelings and expecting everyone to celebrate, or does he realise that this may be hard news for you and is ensuring that he and others are sensitive to your feelings in this?