If that was the case they should have no reason to want reviews at all, traffic to their site is going to consist primarily of people coming to see information on movies and if they get a reputation for that being unreliable, they will lose traffic.
Note also that not all review bombing needs to be political in nature. Suppose one movie company got the bright idea to pay socks to downvote all their competitors movies and boost their own, this is something an honest review company would need to take note of and correct for, because, again, if you're providing review aggregates as a service your user base is going to want to know they're being fed real numbers and not gibberish.
That's not to say the current situation isn't all kinds of suspicious of course, just that in principle, anybody providing a review service will, in fact, have a valid interest in protecting their reviews from bombing attempts.