Elizabeth Warren's comments if true , as reported by Collins, are indeed shameful and disgusting and tells you what sort of president she would make, not that anyone need worry about that.
McConnell's comments on the other hand were merely procedural as the head of the republican senate and he was discussing how the defense of the president in the impeachment trial would be handled (whether to just have an up or down vote or to call witnesses, etc.) which is his job as he is the ranking republican.
Susan Collins shows a disturbing lack of understanding or a cynical attempt to save her own political skin by playing the McCain card, playing the impartial so hard she can find fault with Mitch McConnell where there is none. What is Susan Collins thinking about?
It is his job to defend the republican president.