And Democrats reject Republican bills before they come out. This isn't anything new.
Have you noticed that, over the years, many Democratic and Republican candidates have said things like, "I will bridge the aisle to get things done." Guess what? It never works. People often believe that their own view on a topic is the only correct one and rarely put a significant amount of effort into understanding opposing views. Instead they watch news sources and read blogs that reinforce their own views. The belief that their own view is the only correct one makes people feel that any compromise related to the subject is the wrong thing to do in that situation. In other words, crossing the aisle to work with the opposing party is a nice campaign selling point when thought about it in an abstract manner, but the politician's constituents and financial backers rarely actually want that when presented with a real world scenario or bill. Furthermore, in these situations, compromise by a representative is often viewed as a sign of weakness by his/her supporters. Weak politicians that do not do what their financial backers and constituents want will not be reelected.