the two things, anti-rockism and Pop-ism, are not the same. Pop-ism, to the extent, that is an -Ism (literally rockism turned inside out) could be said to actually go against the goals of anti-rockism, because the latter in its purest sense ought not to rest until all values and beliefs are in tatters, or at least held only provisionally

but various people in these arguments will use the anti-rockist critique to demolish all the rock values, while (switching to affirmative mode) celebrating Pop-ist values (shiny, bouncy, happy, etc) when stating their musical preferences e.g. one guy sez "Abba is greater than Velvet Underground", that's a credo, and credos are what anti-rockists are (supposedly) aiming to unravel

but they switch back and forth depending on which argument and who they want to defeat or deride

really the struggle ought to be between anti-ISM-ists and ISM-ists (rockists, nu-rockist, pop-ists, salsa-ists, rap-ists, junglists)