This comment equates to saying “I don’t care what you think”, and is a perfect example of something that is literally never justified to say on a forum where you have no requirement to interact with them.

If you don’t care what individual people think then simply don’t talk to them.

That's not the rebuke you think it is. You made a claim (not original, I've read it before), someone expressed doubts about your claim (which if proven false, will have dire consequences) and you cannot wave it off with "there are no guarantees in life".

Sorry, you made a claim, there's good reason to believe your claim may not pan out, and if it doesn't the consequences are dire.