Everybody has the right to an opinion and express it, even when somebody else thinks it's nonsense, even when it *IS* nonsense. But who am I (or you or anybody else) to say? This could lead to a (nonsense and endless) discussion, and probably many, every day.
Only in very extreme cases I would delete comments, for example with deeply hating and repetitive insults or if security of any individual is in danger. In most cases I would leave it, just for the sake of free speech versus censorship.
The same for bad ratings, this is just a matter of personal opinion and basically there is no right or wrong. Only when it looks utterly ridiculous I would delete it, for example when a bad rating is just a matter of competition or childish revenge or so. Btw, I didn't see any bad rating on that subtitle.
So I am gonna leave it like it is.