No, he can absolutely disagree when it comes to political questions. That's literally what they're elected on and the point of indirect democracy is to have ded

No, he can absolutely disagree when it comes to political questions. That's literally what they're elected on and the point of indirect democracy is to have dedicated people who can exercise their own judgement using their expertise and resources alongside reacting to constituent concerns. And constituent concerns are not in fact always valid for that matter. Or one set of constituent priorities may conflict with another set. Balancing that kind of thing is a political question. An honest rep's office should certainly take some time to respond to an actual letter and if they don't agree or just plain can't do something give a brief reason as to why (fresh for a new issue raised, could be canned if it's a frequent question but should still represent updated reasoning). But doing so is not wrong. If enough constituents disagree with that, the remedy is to vote that rep out (which would hopefully be easier for outrageous cases like this which do not fall along any typical partisan lines).