I think what frustrates me is that I see these people as, for lack of a better word, "posers". I'm no functional expert and I'm just in the beginning of my career, but I'm very skeptical of devs who had little problem with imperative/OOP code suddenly writing Medium articles saying OOP is dead and "functional" is the "next" step. Just makes me uncomfortable, but I'm learning to ignore it.
I love both FP and OOP and especially love using them together. I honestly don't get these arguments.