Here's a fun game. Try searching 'huge idiot' on Twitter:
It also works with 'huge asshole'
Here's a search for 'the best'
And 'my hero'
Aaaaannnnd back to 'moron'
Or 'racist asshole'
Twitter did not immediately return a request for comment
But, if I had to guess, I'd say that Twitter search leans on keywords commonly associated with each user. If that's the case, this is happening because these people are often described viciously by many of the site's users.
These results, then, would say as much about the makeup of Twitter's user base as they do do about how Twitter search works: that they're probably left-leaning, or at least VERY partisan; sometimes call people names; love Justin Bieber; and really, really don't like Donald Trump.
It does appear that search results are somewhat tailors per-user. But my search for "moron" returned the same list whether I was logged out or logged in.