If someone joins the pool with a big hash rate and stays for 6,8,12 hours, that's not a pool hopper.  The ones I, and the miners of the pool, don't like are the people who jump in a few seconds after we hit a block and mine for 1-2 hours and leave.  They grab a majority of the % and then let everyone else stay around and do the work to find the block and they get an easy payday from it.  It's considered cheating the system by pretty much everyone except the people who do it.

Those are the only people that are not welcome.  They can take us off their list for their bots to use and everyone will be better off.  If they keep doing it they will be taxed to the point they won't waste their time trying to cheat others.