IMO and IME more people are either deliberately disablist or just completely thoughtless than we think.
I am visually impaired. When I was about 7 one of my aunts went out one summer day and bought a swingbal set (anyone remember those?) for all the cousins. Obviously Swing ball is completely visual so wasn’t anything I would have been able to do. Now in the scheme of things I would have said that was just thoughtless and tbh I wouldn’t have given it much headspace. However, one of my cousins was still only a baby and obviously wouldn’t have been able to play either. So my aunt showed up with this swing ball set, and another toy for my cousin so “she doesn’t feel left out.” (She was less than a year old at the time,) so it was blatantly obvious that I had actually been left out. Completely thoughtless but it still happened.
Another time I had a friend in our local area and another family were on holiday there. They were going to be the beach and asked my friend if she would like to go with them. But there was no invite for me. Friend’s mum said emphatically that she wasn’t allowed to go, that they either take us both (I was there at the time the invite was made) or they take neither of us. And so it was.
And for anyone saying that my friend was punished for me not being invited, her mum was very much of the view that friend needed to realise that it’s not ok to exclude people on the basis of their disability.
Deliberately not inviting a disabled person to the wedding because the bride thinks they might behave inappropriately is not ok on any level, and tbh would possibly even be a deal breaker in the relationship for me. Because the reality is that this disabled person has probably been discussed before. You don’t have a 20 year relationship with someone and then suddenly decide their behaviour is inappropriate, this won’t be the first time he’s been discussed.
Interesting isn’t it that people become offended that people don’t want to invite their screaming tantruming children to weddings, but excluding a person with a disability is seemingly ok.
I would decline (and I wouldn’t be all that polite about it,) and I wouldn’t send a card or a gift. And if that created a family rift then so be it.