No one suggested that surveillance is as bad as cancer. All that was said is that blocking Facebook dating has a similar effect on surveillance (in kind, not in degree) as banning tobacco has on cancer.
Is that even true? Stopping smoking reduces the risk of lung cancer by like over 90%, blocking Facebook doesn't change the fact that the Chinese and American spy agencies are still doing everything they can to record all your emails and personal communication.
Degree matters, because the harm from censorship and restricting people's choices is a matter of degree, and if the harm avoided by the ban is a lower degree then it ends up as a net negative.
If it wasn't for companies like Facebook using and thus requesting that information to begin with, it would be a hell of a lot more difficult for American and Chinese agencies to get your data.
Nobody is going to suffer any noticeable or concrete harms because Facebook launch a dating site of all things. The reaction here is wildly out of proportion to the scale of the problem; assuming there's any problem at all (everyone with a Facebook profile made one, they wanted to be there, so there isn't).
Degree matters, because the harm from censorship and restricting people's choices is a matter of degree, and if the harm avoided by the ban is a lower degree then it ends up as a net negative.