Absolutely people take politics into account when deciding to see a movie. I don't think there is anything wrong with that at all.
I suspect that RT was surprised when that feature was used the way it was. Politics was probably not what they are thinking about. They are just trying to provide a review aggregator. I doubt they really though through the implication of what "I want to see this movie" might mean.
How could they fail to realize that a measure of whether people wanted to see a movie would not be reviews of the movie? I think the possibility they failed to consider is they might find themselves in a political disagreement with the users of their site. Still, it's a wonder how they could have failed to anticipate that after the debacle surrounding the recent Ghostbusters movie.
I suspect that RT was surprised when that feature was used the way it was. Politics was probably not what they are thinking about. They are just trying to provide a review aggregator. I doubt they really though through the implication of what "I want to see this movie" might mean.