It sounds like you had no idea he felt that way...which if you look at the bright side shows that he cares enough to not even show that they annoy him, and he cares about you enough that he is willing to be around them and be pleasant for the sake of the relationship. The FB support group might literally be...well, a place for support for him. He can vent, get it off his chest, and go back to loving you. I’m sorry you had to find out he doesn’t care for your kids, and hopefully the situation gets better for everyone.

I suggest you have a non-confrontational talk with you husband about your family - When the kids aren’t around to hear what is said. Obviously he has some issues. It would be wise to understand what those issues are and see if they can be addressed. While some might say your husband was just “venting” in a harmless manner, I think this exposes a basic issue somewhere. If you don’t understand the dynamics of what’s going on, someday you may get an unpleasant surprise if it all becomes too much for your husband. “Instant families” are not always easy to deal with. My teenage son from a prior marriage came close at times to causing fractures between my now wife and me. Frankly he was obnoxious and a trouble maker and not of a personality that my childless girlfriend and later wife wanted to deal with. He was difficult enough for me to deal with and he only lived with me on alternate weekends at the time. I’m not saying your children are like that, just that there can be frictions that can strain a relationship. Either accommodations will be made or eventually it may prove to be a serious problem. Before that happens family counseling might be in order.

Don't worry about it -- nothing bad has ever happened because of Facebook groups. The company monitors groups and shuts them down if anything bad is going on, even if the company loses revenue from that.

As someone who dodged being a stepdad, I find this pretty hilarious.

No rule that says you need to love or even like your step kids.as long as he doesn't lash out at them or is generally mean to them.You can not like someone and have enough respect to do right by them.

some dudes will play dad just for some puss, the desperation

Kids are pretty awful and life draining, I can't really blame him. I'd do the same thing lol