Google would say no because they always present the most valuable ads first (highest payout * clickthrough rates). Some webmasters would say yes because they see revenue increase when they do.
I've filtered those ads which are directly competitive with my site...But I think those were the high paying ads cause now my ad revenue is down
I only filter ads that are blatantly irrelevent to my content or potentially offensive to my audience. Otherwise, I trust Google to display the best ads.
Best way is to block all the scraper websites. If you need i can give you list of websites which i have blocked. And i am sure these websites are harmful for every webmaster.Because these websites are totally BS.