Why do masks make people so angry?

I still mask, I think COVID is super serious and I work with immunocompromised patients in a hospital, and I take public transit, so it's just generally a good idea. I am very, very, very vaccinated, but I'm still not comfortable unmasked. Two angry men on separate occasions have made comments to me about masking and how I don't need to do it. I just stare right through them and ignore, but why are they so angry? It does not affect them in the slightest, and if they think I'm stupid have at it.