I have never heard a Rov who says someone who eats Chalav Stam is eating TREIF. You rav might have said you cant eat it, but he would never say someone else who eats it is eating treif. He would likely say its ok for him , but not for you.
If that were the case then the O-U , O-K etc would not be considered kosher since they do allow it.
FYI if you have ever been to a dairy farm you would see there is no such thing as Chalav Akum, Chalav Yisroel etc. NOBODY milks cow anymore. Its all done by machines and automation. Some metal pipes are placed under the cows Utters and these pipes are only made to fit a cows utters, no other animals. The Milk is then pumped out and send to this giant vat or bottle and there is no way to add anything to the vat. The Milk is then pumped on a truck to the factory.