People cannot be free to make good choices if they are prevented from knowing all their options. (By the same token, scamming, lying, etc are immoral.)

it goes against freedom of speech

and it stops people from being able to judge and make their own decisions about things

and it can alienate people by hiding anyone who shares a similar view to them

all these things are abuse of a person, so it is immoral

Anything that can be censored can be considered art, art is free expression and it is wrong to censor free expression.