"Crashing at Kelly's house isn't acceptable" is reasonable because of the potential for problems... it's not a public activity.

But if crashing at Kelly's is something that you have always done, why does this need to change because of an SO? Should they not just have faith in your judgment ability and control of the situation? For example, sleeping on Kelly's couch, vs sleeping in the same bed as her - the former being acceptable, the latter being crossing a line. This should just be acceptable by default.

If your SO expresses extreme discomfort on the situation, that is their insecurity and lack of trust in you. They are taking your freedom / independence away, which I believe to be a very important part of any healthy relationship, by demanding change in your dynamics with friends.

Example: I'm still friends with a girl I briefly dated. We never hit it off more than friends (there was no 'activity'). But my wife wouldn't be ok with me sleeping over. Fair enough. I have no reason to do so. It's a reasonable compromise. However, if she said I should never talk to this person again, that would be unreasonable, and pushback would commence.

So this example kind of ties to what I've laid out above. I would want my SO to be able to sleep over at other people's houses, because I want to give her that freedom. I trust her judgement to not cross any lines. I don't think that's a reasonable compromise at all.