Kicked out Christmas evening without our coats or keys due to autistic sons meltdown.. AITA?

Two nights ago we were invited to my fiancés dad’s place for Christmas dinner. His dad & his girlfriend live together & she just moved here last year and I’ve never had any issues with her before. She states she’s a respite licensed respite worker, I’ve explained in detail I have a son , 15 with level 3 autism. So when they invited us I figured things would be fine if we had any issues she should understand, not to mention she was warned and insisted we all come together . Things went great for the first 45 minutes. My son was calm and not giving any signs of stress in the new environment. And he’s usually good for visiting people anyways especially if food’s involved. He ended up going to the bathroom about 45 minutes into the event and he was in theee for while so I went to check on him . He was wash in his hands and stopped, started to disrob , had nothing but his underwear on , I insisted he put his clothes back on because he knows we don’t do bath time at other peoples homes we aren’t staying at ( she had a jet tub, he loves water and he wanted to use it ) . I tried to redirect him with a few things he liked to distract him but nothing was working and he ended up having a meltdown. He ran out of the bathroom , into the kitchen , where I started to calm him down and get him to put his pants on .. dads “ girlfriend “ came into the kitchen yelling because she thought he was going to hit me when he moved weird ( he didn’t try to hit me ) which resulted in the meltdown escalating when I had started to defuse it. Her screaming caused everyone else to come into the kitchen , so my son ran to the porch area , knocked on the window a few times and was swinging at us to get the others to back away .. she started screaming at me and him to “ get him out of here , he’s trying tl smash my window “ .. he wasn’t , he just knocked On it three times and left it alone . The screaming this over and over along with “ why isn’t this kid medicated “ was causing him more anxiety clearly cause he would start listening to me then hear her scream ar him to get out . While trying to get his boots on him and grab our coats she yelled thah he didn’t need that to get him outside .. we ended up pushed out the door with boots only , no wonder coats ( it’s dead winter here ) at 6pm. No keys to get in the car . I snapped Before going out the door and told them not to worry about it we would get out alright . And they are trying to tell my fiancé now that my Son has issues , needs to be heavily medicated , etc .. over one incident that Farley happens during meltdowns. He doesn’t usually get like this but the yelling and screaming and hostility seemed to cause things to escalate beyond what is usually normal for a meltdown. They think I was being rude by snapping at them. AITA? I’m upset about this situation, about how we weee treated . They don’t think o should be and I should be sorry ? What do guy guys think.