Is it? I haven’t studied philosophy (but I have studied math) - it seems to me that the Wikipedia article on Truism demands the statement to be true for it to be a truism. But it’s not true though?

The way I see it, the statement can be construed as:

I’m not allowed to criticize X -> X rules over me

But, perhaps because “allowed” and “criticize” are subject to interpretation, there are plenty of groups you will be socially penalized for criticizing (see jokes about kids with cancer below the comment with the quote - I can’t figure out how to link to them). Many countries also protect minorities by making hate speech illegal, and yet those minorities are not ruling the country (though that’s probably exactly what the quote was originally meant to imply). If anything, the truism would be the ‘opposite’ implication:

X rules over me -> I’m not allowed to criticize X

Yet even this isn’t categorically true, like in democracies (which I guess brings in the interpretation of “rule”, as well).