I think it was the "hippie" epithet that upset people (using the name of a group of people as an insult, on top of the original insult, is not likely to go well

I think it was the "hippie" epithet that upset people (using the name of a group of people as an insult, on top of the original insult, is not likely to go well here). People who advocate for shorter work weeks are genuinely concerned about the big picture, long-term effects of overwork. You might get more traction if you recognize that and explain that maybe they're missing some essential little picture, short-term details, rather than dismissing and insulting their views.