Writing off or blindly endorsing someone because of party affiliation is an absurd outcome of lazy thought. After all, in this case, it is clearly Republicans of good conscience who have been intimidated by dark money.
Maybe I am missing some larger point here or don't fully understand because of a context that you have not explained, but I don't think writing off or endorsing because of party afilliation is lazy thought. Rather, it is very pragmatic.
Back in the late 80s and early 90s, televanglists were all about spinning record alblums backward to see if there was back masking which in there mind made the alblum satanic. All they had to do was read the label and it said AC/DC highway to hell. (not that I believe AC/DC is satanic or that saten even exisits)
The same is true of political partys. Yes, you can go on a witchhunt to find out who has been "tainted" by Koch Bros. or AFA or whatever group you believe demonizes political representatives.
The truth is each party has its platform and if a person runs under that banner they align themselves with the policies of that party. The best way for republicans to rid their party of the influence of Koch Bros. is to paint them in that corner, until they get sick of it, push back, and reform their party. My objection is to republican party ideaology and outside money is only a secondary consideration.