Would you say there kol haposel? I assume not.
Of course not. In halachah, we do weigh the gadlus of poskim when determining who is correct. Without even knowing the issue, I will say that R’ Moshe is right (especially since he uses such strong language.)
Similarly, Chacham Ovadiah zt’l gets enough credit from me (as if he needs my haskamah…) that when someone of lesser stature (about which you seem to agree with me) ch’v says what he does, I take sides with Chacham Ovadiah and call “Kol haposel” on the other fellow.
But of course, Kol haposel is not a universal rule, you have know how to apply it. And, as you seem to agree, there is an earned hierarchy in klal Yisroel.