And why would that be? That message is basically a feedback request. They are attempting to address a legitimate issue that may cause them a decline in viewership and resulting revenues.
If, like the Democratic senators who signed the letter, I enjoyed mostly glowing media coverage, I suppose that I would be upset when a company dismisses that glowing coverage as being the result of bias - even if I knew they were correct. But that’s a hardly a reason to abuse your power as a senator to attempt to damage the company that is doing that, especially when they are trying to solve a legitimate problem for the public at their own stations. That’s pretty evil if you ask me.