Comment by entropicdrifter

Then say that.

If someone goes on to say, "well you ruined my vacation" or something like that, they weren't asking at all, they were demanding and now they're bullying you about having boundaries to try to tear your boundaries down.

People who go out of their way to try to trample your explicitly stated boundaries are abusing you.

So say no, and if they don't take it well, create distance or tell them off. Avoiding conflict in this case is fully to your own detriment.

If, on the other hand, they do take it well, then guess what? They're an asker and are just fully exploring their options and it's no big deal to them that you said no.