I think everyone with a working brain will know that once this sort of vetting starts, it will usher through a host of other keywords that they will search for.
But let's forget that for a second, and talk about the present. How do you define an "activist"?
Lengthy blogs on certain topics?
Heated debates on facebook?
A temporarily "I stand with Palestine" profile picture?
A facebook like on any newspaper article that's negative toward Israel?
My problem is we have no verifiable visibility into the process. If this were a rule banning anyone who has a recent history of advocating for violent organisations, e.g. Hamas, or even performatively-disruptive modes of protest, e.g. bridge blocking and breaking into buildings, I'd be okay with that. I'd disagree. (In part due to hypocrisy. The January 6th rioters broke into the Capitol.) But I'd accept it as validly promulgated under our system of laws.
As it stands, I have no faith that someone with a "fuck Elon" tweet won't be barred from a PhD programme.