When people are talked down to, they often dig in their heels due to an emotion called psychological reactance. The reactionary ape that still exists in every human feels challenged and that ape will not allow reason to stop it.
If you see such a reaction and allow yourself to believe “well that person was just an immature child”, you risk giving yourself license to keep talking down to people. Repeat ad nauseum.
It doesn’t matter that you’re objectively correct about the effect meat has on the biosphere if you just keep going around that circle, creating 0 new vegans every lap