If I were able to convince a large swath of the population to participate in a suicide ritual a la Heaven's Gate, do you think that it's wrong to quash the spread of that message on the internet?
It is not wrong for websites to restrict certain information by their own choice. It is wrong - unconstitutional, even - for the government to force them to do so. You should read a bit about Brandenburg v. Ohio, 395 U.S. 444 (1969) [1] and Hess v. Indiana, 414 U.S. 105 (1973) [2]. (By the way, suicide is not lawless action anyway. Whether advocacy of it is lawless is a different matter, but likely free speech.)
[1] https://en.wikipedia.org/wiki/Brandenburg_v._Ohio
[2] https://en.wikipedia.org/wiki/Hess_v._Indiana