I think you are saying that Libs are motivated to ignore the positives of Trump because they are upset that Trump won. This is the logical fallacy of Appeal to Motive.
Here is how that is a fallacy: Why not then assume that those who were happy Trump won cannot see his negatives? Why would it work one way for one side but not the same way (in reverse) for the other side?
The second problem is it is an overgeneralization. Are all Libs guilty of this because Trump won? If they are not all guilty, are some correct in what they claim?
A third problem is knowing what motivates people. How can you know this is the motive for Libs? Did you do a psychological test? I think not.
A fourth problem is that it's simply an attack on the character of Libs. 
And the final, 5th problem is that it does not address the original assertions. If I say you stole the cookies and then you say, "well, you say that because you wanted them", how does that dismiss my original assertion you stole them?