Are those who are relying on Rav Moshe to justify Cholov Stam as quick to follow Rav Moshe in his other psakim where he is likewise somewhat of a mechadesh and a minority opinion? For example, do they refrain from eating Wise Potato Chips since Rav Moshe held there was a Bishul Akum concern (as per his son that Rav Moshe did know what potato chips were, and was indeed referring to them)? Or what about automating things in the home other than the lighting on shabbos and yom tov? Or is it only when it is convenient to follow Rav Moshe because that Häagen-Dazs is creamy and delicious?
This is a poor argument.
That would depend on what their argument is. If they are simply saying that the minhag in America
was to follow Rav Moshes psak on Chalav Stam at the time when they were maybe a dozen chalav yisroel products but that still holds true today when you have hundreds and perhaps thousands of products and it is at best a minor inconvenience to eat chalav Yisrael, one would have to know if that is a valid argument. There are many things that Klal Yisrael was not makpid on when times were difficult that have completely changed as the situation changed, such as hiddurim in mikvaos, buying lulavim for each child, and many others.
On the other hand, if their argument is that Rav Moshe was the preeminent posek in America so we should be following his psak, minhag or no minhag, then what I wrote above is absolutely valid.