Question Part I
I am obviously not an expert on the subject but I was always under the impression that there are in fact some legitimate and reputable poskim who would allow kohanim to visit certain kivrei tzadikim even though I have raised many eyebrows by saying that.
Answer Part I
There are several Rishonim who say this.
Question Part II
Am I completely mistaken? I know you have told others not to go, but is it wrong to say there are poskim who matir. I have seen firsthand kohanim duchaning in a couple of these places. Are they just misguided? A Rabbi once showed me a Shem Hagedolim who says that kivrei tzadikim are not metamei and in that piece there he brings a rayah from the Gemara in Kesubos “Yom Shmes Rebbe Batlah Kedusha” and Tosafos there (Kesubos 103b). I know there are numerous other rayos and haaros in the Shas and poskim lkan u’lkan but what is the bottom line?
Answer Part II
I would consider it a minority opinion in an issur torah.