Also, please keep deep resentment off HN. If that's how you're feeling, find some other way to process it before returning to comment here. (Edit: I know that's not easy, but it's necessary for this place to not burn.)
And that's usually the end of the comment. There's no explanation of why X and A are like each other in any way that matters. There's no conclusion, like either "Since I presume you're not in favor of X, you can't consistently be in favor of A either", or the opposite, "Since you're in favor of A, you really ought to reconsider your position on X".
What there is, though, is what feels to me like an attempt to put words in the other person's mouth. This feels to me like a step beyond whataboutism. It's not just "what about X", it's "You must also agree that X is true".
I've been seeing this pattern increasingly over the last 6 to 12 months. (Alternately, I've become more sensitive to this pattern in the same time.) I consider it to be... let's just say it's not a positive contribution to the discussion.
So: How should one respond to this? Flag every instance? Ignore? Simply respond "Non sequitur" and leave it at that?
You don't like how I responded. Fine; you have the right. But what do you think I should do instead?
There's a difference between the government trying to take it by spying, and the government forcing you to give it away by contract as a condition of doing business. One you can take countermeasures against; one you can't.
That cuts not only the first two paragraphs, but also the flamey bits from the third ("Apparently you can't see" and "Hint:"). Doing all that yields a substantive, respectful reply. (I'm not considering whether it's a good argument here—just whether it's offside or not.) And of course it's fine to ask politely for the other person's source, or how they know what they claim.
The general answer: one good way to reply to a comment of the form "If you are in favor of A, then you must also favor X" is to mention significant difference(s) between A and X that show why A doesn't imply X. For example, something favorable in A that X lacks; or something unfavorable in X that A lacks. And to show why the difference is strong enough to break the assumed arrow from A to X.
There's an aspect to this that is unfair. pinkfoot's comment was pretty lazy (opting for snark and a drive-by rather than giving the reader enough information to really establish anything). If you're going to reply to a comment like that, the temptation is also to take the path of least resistance—for example, to vent, rather than to put much thought or work into a reply. The other person didn't put much thought or work into theirs, so why should you?
The answer is that you don't owe it to the other person, but to the general reader and the community. Your reply to such a comment will either raise the quality of the site or lower it. (Responding on the same level is lowering.) The two good options are: put in the thought and work to come up with a specific reply—cutting any flamey bits because by then you don't need them and they weaken your case anyhow—or, if you don't have the time and energy to do so, simply not to post.