First of all, they are absolutely wrong in assuming that this bear market would have any real effects on bitcoin in the long term. Bitcoin has experienced several bear markets before, and it's normal across all asset classes. It's only something short term, and won't really extend beyond that.
Also, I think that these people are misinformed about bitcoin, probably hasn't even bothered to research in depth into the concepts underlying bitcoin, and using "environmental activism" as a way to push their stance.
I think Hydrogen has already debunked this "bitcoin is bad for the environment" myth in one of his posts. The fact of the matter is that it doesn't matter whether bitcoin mining is taking up x amount of energy, as long as the energy is sustainably sourced, it doesn't matter. Besides, excess generated energy would have gone to waste anyways. Also, bitcoin's not just wasting the energy. It's using it for a purpose - and probably more efficiently than gold mining, bill printing, etc.