Didn't get that way in a vaccuum :)
If he's a wonderful man, he likely had a wonderful mother and eventually, that same woman is going to be the grandma to your children.
It sounds as though you're probably right to be angry, I can tell you believe you're right but where will being right get you when it means your mom-in-law won't be coming to her son's wedding?
There's a compromise to be made by the more mature of the two of you. You only win by being the more mature one. This isn't a relationship until the wedding, it's a lifetime relationship and if you don't sort things out now, it can and probably will spoil your marriage.
As an old married woman, I can tell you that parents and in-laws often do give constructive help and input. I can also tell you that there are only two people in a marriage if everything else is going well. When you have a situation where his parents or your parents aren't coming to your wedding, that sits between the two of you like an elephant in the room.
You don't have to be a pushover ... you can think over the things your MIL and SIL are revved and excited about and see if any of it can be incorporated into your wedding or life. You can remember that this is just as difficult a time for them as it is for you, especially since you all aren't getting along. They are losing a precious relationship with their son/brother if this doesn't work out.
You don't have to apologise to smooth things over. You could call the three of you together to talk and try to work things out. If you maintain your calm even if they lose theirs and bring them back on point, you could end up forming one of the most precious and valuable relationships you'll ever have.
My mom-in-law and I couldn't be more different but I treasure her because she raised my wonderful husband into the man he is. She spoils my guys rotten and sometimes lets them do things I don't agree with but I already have the proof she's an awesome mom so I go with "nana's rules" at nana's house and mom and dad's rules at home. (I had the same arrangement with my parents when they were also spoiling our guys rotten)
When I was getting married, I was the centre of the universe and in hindsight, I know I made some horrible blunders that could have ended up with bitter feelings on my mom-in-law's part and I would have figured she was just trying to ruin my wedding. Now I treasure her more because she was the one who let it slide to keep a good relationship. You don't have that so you'll have to do the work but it's worth it.... I know it's worth it.