First, whatever they and a majority of the public believe about the repugnancy of the president’s comments, they believe Trump was duly elected as president on the Republican ticket and that he retains a deeply loyal following within the party. They are reluctant to go against that Trump base.With regard to that second point, since his January inauguration Trump has accomplished much more than the legislators. He may have pissed off a lot of people but he's moving forward: appointing judges, killing excessive regulations, making executive branch policy. The Republican majorities in both houses of Congress? Not so much.
Second, however personally upset they are by the president’s remarks, many lawmakers believe they must maintain a working relationship with the president if they are to accomplish their legislative goals — including tax reform and even health care. So far, they have little to show for their work this year.
Donald Trump effectively said to Mitch McConnell, Paul Ryan, and their minions, "Lead, follow, or get out of the way." Having proved incapable of leading, they reluctantly follow.