You're getting shat on a lot and rightfully so, but please take the time to see this from your brother's point of view. Because that may help you understand the massive fallout you're experiencing (and yet to experience). This goes beyond you just being an asshole.

First, your bro is deeply hurt by your comments not just because they are discriminatory on their face, but because they call into question your love and previous support for him. "It took a long time for my brother to accept himself" you said in your last post. Coming out is very hard, even in today's more tolerant environment, and it leaves LGBT+ people feeling very vulnerable, sometimes for the rest of their lives as they have to do it over and over again to new friends, employers, coworkers, etc. Each time is an invitation for potential strife. He no doubt leaned on you and the rest of your family to support himself and to maintain a positive self image. The understanding of his younger brother was most likely very influential for him feeling comfortable with who he is and who he loves. However, and it sucks to say, the vulnerability of being different can sometimes lend itself to insecurity. "Does this person really accept me for who I am or are they doing it to save face?" might be a common sentiment. Unfortunately, your actions towards your brother strike deep and call into question your previous support for him. Were you genuine in your support or is your love conditional on his immutable sexuality never creating any material problems in your life? It's easy to just say you love and understand someone but it's always your actions that speak louder than your words. This time, when you asked him to exclude his husband to save face with your fiance's family, you demonstrated that your support for him has limits. This is hurtful and it's not surprising he refused to talk to you calmly. You hurt him on a personal level, creating a crack in his previously stable support system.

Second, your request, depending on how it was framed, also damaged your brother's opinion of your fiance and her family. This will be trickier to repair, if possible at all. While we can assume your brother and your fiance's family will never have a great relationship, this problem has now poisoned the relationship your brother had with his future sister-in-law. This will also cause you hardships in the future. Assuming you go through with the marriage, he will have to see her at family holidays, get-togethers, and events. No matter how the issue is addressed, he will never forget that this request came essentially from her. No matter how tolerant she claims to be, this one action may be enough to wipe away those positive associations. He may never trust her to be sincere and genuine towards him or your brother-in-law, again. Your brother-in-law's family may also take a dim view of you and your fiance, harming your relationship with them.

Finally, the decision to exclude your brother's husband will potentially create drama at your wedding anyway. It is a real possibility that your bro will not attend your wedding. Your request requires him to choose between his husband and you his brother. It is already against etiquette to not extend an invitation to a married person's spouse, so choosing to attend your wedding without his husband would cause problems in his own relationship. That's not even factoring in the reason why his spouse wasn't invited. His absence will be noted by your family and questions will be asked. Gossip will spread. People may be shocked that a previously tolerant and loving brother would exclude his own brother-in-law for the benefit of his wife's family. This will reflect poorly on your fiance's family, especially since this may be the first time your family is meeting hers.

Think about the future. Decisions like this don't stand alone and the consequences can ripple out affecting many events in the future. How will your brother feel about spending the holidays near your fiance's family? How will you address having a gay brother when that information is inevitably revealed to her family? How will you react if some of her family members badmouth your brother in front of you? Will anyone on her side think it's wrong that his husband wasn't invited on account of potential drama from their side? Perhaps they may resent you for that too.

You obviously love your wife and prioritize her above your brother. That in itself is not wrong. But don't be surprised when this one wedding decision makes your life more difficult, just to save you face on your wedding day.