It's a thread about a Linux distro and further a thread about some complications one might run into versus others. If someone's concerned about a problem with pre-compiled proprietary software, particularly one you know they'd rather not have either, jumping in with a Har Har try not to have that problem isn't ... well it's just flat humor. Nothing mean or bad just, downvotably flat?

I don't think it's any sort of Mac generation downvoting, I think it's more the opposite: they're preaching to the choir. Yea. We Know.

The real question is, when did "don't use proprietary software" become an acceptable thing to say to people?

Since around 1975-80, when software makers stop'd giving you the source-code with the license to use it, and just gave you the compiled unchangeable product?

Not is it just acceptable, it's your obligation to tell peoples what the downside (or upside) of closed down software is. Is a closed source webserver a good idea? probably not. Is THE closed source Photo-editing program a good idea? Probably yes....if you really need it.

Mac generation? Maybe if you mean those whose first computing experience was with microcomputers in the 80s. Every single program I used for the first ~14 years (1984 to 1998, when I first used Linux) of my computing experience was proprietary.