Once set the example of impeaching a President for what, when the excitement of the hour shall have subsided, will be regarded as insufficient causes, as several of those now alleged against the President were decided to be by the House of Representatives only a few months since, and no future President will be safe who happens to differ with a majority of the House and two thirds of the Senate on any measure deemed by them important, particularly if of a political character. Blinded by partisan zeal, with such an example before them, they will not scruple to remove out of the way any obstacle to the accomplishment of their purposes, and what then becomes of the checks and balances of the Constitution, so carefully devised and so vital to its perpetuity? They are all gone.
-Senator Lyman Trumbull
Wise words stated 150 years ago, and they are just as valid today.
The president is a check on the Congress, and you can't impeach a president for being "Orangemanbad" and disagreeing with the way Congress normally governs without destroying those checks and balances.