I'm happy to be blocked from products that aren't compliant. There will usually be other alternatives. This is better than unknowingly using something that could cause me problems later.

I don't even take it as an aggressive negative, unless it is explicitly expressed as such. You can just be honest and say "I can't accept your custom at this time because X, and we have other priorities that would make addressing X to everyone's satisfaction a problem for the foreseeable future".