If a question is scored at -4 or below, it doesn't show up on the front page of the site. This is current functionality
When a question is migrated to another site it is locked on the origin site. This means there can't be any voting on it. Sometimes / often when a question is blatantly off topic on a given site, it gets down votes. Once the question is migrated, being locked, it can't get any more votes that may make it not show on the front page.
Change the threshold for locked questions (of which migrated questions are a subset of) so that negatively scored locked questions don't show up on the front page.
Do note that the front page is different than the 'questions by activity' or 'newest questions' which show all questions no matter what their score. This is just about the front page that you get to when you go to the site.
The question came up for "why not extend this to all closed questions?" The answer to this is that there are situations where you want eyeballs on a closed negatively scored question - and for that to be shown on the front page. In particular, situations where a mediocre question had an edit to make it better (and get reopen or up votes), or a stealth spam edit was done to something. While these would both show up in the question activity tab too, locked questions are a special case in that neither of these situations can occur. There is nothing that can be done with a locked question, other than follow its migration if that was the reason for a lock.