I expressed my view against the association bonus being granted on MO already in older discussion and upvoted the feature request.
However, some points to make my view more precise:
I agree the main issue is voting, so one could also ask for less of a reduction, that is just no voting with association. In fact this request exists on meta.SOrequest exists on meta.SO presented by Mad Scientist about a month ago. It could also make sense that those that care about it, voice there opinion there too, or at least vote on it. (I did not yet myself, but I think it is as simple as just login in as on MO and then one can vote due to the association bonus, somewhat ironic, though not quite as the meta.SO is a special case for a site.)
For some other things I now think it is somewhat reasonable. I did not yet say anything on math.SE but created an account recently, the actual motivation was to test something as a low-rep user somewhere, but also I could imagine to say want to say something on a question after it was migrated there, and then it would feel odd if I could not comment there, so there is some sense to this association thing, too. (Sure I could get the points otherwise there too, but if I want to leave a comment "now" I would be not happy if I could not.)
For sock-puppet voting I see less of a problem. Since for somebody to get something out of having sock-puppets here to vote the need at least to be in some sense in touch with the subject of the site. And, for those it is and also was never a real issue to ask some questions also on MO that would get them two upvotes total and not too many downvotes. (This is according to old rep, the new one is rather harder regarding this, so it is not all bad the changes.) And then we had also some that had some "colleague" ask a question that they then answered, so I would say it was always easy enough.
However, I still agree that for voting in general it is a bit of a problem, as it likely will still give more votes to the soft-ish things that already get too many votes, IMO. But then this is also not a big problem in my opinion, yet it is still a problem although even if only a minor one.