Then how would blocking X be a good thing in the first place?
Because the one deciding to block it thinks it is bad.
Let me break down the take aways points as this is getting tiresome.
1. Your original argument does not work if it is talking about absolutes. Badness is not attributed based on the decision to block something. In fact, I was charitable in my reconstruction of your argument, it should be phrased as a converse error which is a fallacy.
2. You later added the additional information, namely that you were speaking of relatives. This contradicts your original statement that the proposition was false, as this is an absolute claim. This rendered the entire discussion meaningless.
3. You are now asking me why someone would make the decision to block something and how that is a good thing. There are two ways this can be true.
Absolutes: Although, no moral propositions are truly absolute, for the sake of argument we take rape which in America and most of the world is wrong. The decision to block, prevent and deter individuals from performing a rape comes
after rape has been determined to be a moral wrong. Meaning that to block, prevent or deter individuals from performing rape is a good thing in virtue of it having been decided that rape is bad, absolutely.
Relatives: As an individual, I have the right to form my own opinion and act upon the basis of that opinion. If I think rape is bad then I will refrain from raping and prevent rapes when possible. Thus, blocking, preventing and refraining from rape are good actions relative to the individual. My stating that refraining, preventing or blocking rape is a good thing in no way defines rape as a bad thing in an absolute sense.
Your original argument took a relative position and extrapolated that the speaker was stating porn was bad, absolutely. This was made clear by your phrasing and it was a fallacy.
If you are now going to take a relative position and extrapolate a relative position, you are wasting your time as this is plainly obvious.