Do to popular demand, I will list all the OU pokemon (that I use) that check non-scarfed Hoopa-U and forces it out. I never really used pursuit on showdown, and yet it's still effortless for me to put that genie back in its place. Observe:
As you can see, there is no shortage of viable answers to this pokemon. You just got to prepare for it, like any other A+ pokemon. The only reason Hoopa-U might be considered broken is because, like many wallbreakers, it has almost no true counters, but since it can go both physical and special, it especially annihates stall like a predator. Stall is an endangered species, and after Mega Sableye was on trial for singlehandedly saving it, Hoopa-U is on trial for singlehandedly destroying it. It is up to the voters if stall has a right to live, but there is no question that Hoopa-U can be "handled" by non-stall teams.
I think the issue people have with Hoopa-u is the fact that most of the listed Pokemon can't really switch in on it, lest they run the risk of losing over 50% of their HP in a best case scenario... Coupled with the fairly nice movepool that lets it actually do good verses some of its would-be checks/counters it's very hard to throw something in its path that would force a switch without losing a Pokemon, which seems to be the center of the argument to ban it.