Sometimes people want to be generally helped, and sometimes people just want an answer to their question. If the answer is “it’s impossible” then that’s a valid answer, but if the answer is “I’m not going to tell you, instead I’m going to assume that what you actually want is me to teach you why you were wrong to ask the question in the first place” then theres a good chance that actually they just wanted an answer, and you deciding for them what they need comes across as patronising.

I think the talking down aspect comes from phrases like “you shouldn’t be doing X”, especially when these statements are made as absolutes, rather than contextualised with actual reasons.

Running GUI programs as root might cause security problems, or it might cause software problems. And while you might find these issues important, others might not.

In my opinion, saying something like “it’s not a good idea if you care about security” or “doing so might make your PC burst into flames” gives helpful warnings for OP and future readers without talking down to them by making decisions for them what they should and should not do.