Discussion on answer by Kilisi: Is it appropriate to speak up for a team member who can't drink due to addiction recovery when a company event is being planned?

If instead you had said "It's great that you're looking out for your colleagues, but I think in this situation there's nothing that you need to do, other than be supportive if something happens on the night." it would be the same advice, but with a very different tone.

The mention of "go and have a good time" reinforces this: it comes across as "forget about anyone else's problems, enjoy your own life!" which would be a very selfish philosophy.

I think the reason people are reacting strongly to your answer is that it is very strongly worded: "don't babysit adults" has connotations way beyond "right now, there's nothing you need to do". There's a huge spectrum between "babysitting" and "having sympathy for your fellow human".

@Kilisi I wish everybody had that same confidence in saying no to every unwanted invitation. But for a recovering alcoholic these things often aren't simple.