@Maljam It's mostly hard cheese that constipates me. It was my main protein source. With milk, I don't have this issue, but I do have others issues.
I've come to realize that all this talk such as dairy = good, X = bad, is reductionist.
Eat to optimize digestion, energy levels, temperatures, pulse, mood. The challenge is to find the combinations of foods that will do that, given your current state of metabolic & digestive health.
If the opioid effects come from the protein, then it would make sense cheese is more constipating as it is more protein dense than milk (I think I have got that right), or if the problem is too much calcium compared to magnesium, cheese would also be worse too.
I completely agree with your bolded part, I dont think there are any inherently "bad" foods really, but there does seem to be certain foods that people with poor digestion commonly struggle with and should avoid.