I'm not a big fan of Sheila Jackson Lee, though she is my Congresswoman. I've tended to vote against her in pretty much every election but she is unlikely to be removed by her constituents -- and her district was gerrymandered by the Texas Legislature (at least currently) to include most of the areas that vote Democrat on the north side of Houston.
OTOH, without more information, I'm not going to judge her for this. As others have pointed out, there are any number of reasons why United may have done this (when the reservation was made, frequent flyer status, type of ticket purchased, etc). Instead, it seems that the complaint was someone upset at being bumped out of First Class and who wanted to make this political.