Absolutely.
No chance I'd be supporting the club if this happens, and that isn't some kind of overreaction either, and hopefully most fans will feel similar. The reason I came about supporting this club was largely to do with our history and tradition, the way we've stood by our strong morals and integrity, the way we responded to a tragedy like Munich and came out of it together, etc. This isn't selling the club to a random shady corrupt businessman or corporation. It's basically letting one of the most vile and inhuman national leaders take the club in their hands and there's no chance whatsoever I'd support something that's run by those people.
This is Saudi Arabia we are talking about, a place where human rights are a joke, people especially women are treated in barbaric manner, a country that activity takes part in genocide and arming terrorist organisations. Giving an ounce of support to these guys is as good as supporting a terrorist organisation. Takes a second to think about the atrocities they have committed and how no one with a slight bit of conscious would never consider taking sides with these guys.
Obviously it won't be stopping watching football and even United games for that matter, but the entire connection I've had as a fan with the club and the way we are passionate about everything that happens at the club, on and off the pitch would be totally gone. If anything it would be pretty shit watching them win stuff after being funded by blood money. Will be a really sad day and for someone like me who pretty much follows football because of United and little less, it would mean pretty much the end of actively and passionately following the sport itself.