I have read both novels, FWIW. The clear difference between the two is that Clancy's bombers are readily identified as bad people doing a bad thing; they literally betray all of their collaborators, and everyone else identifies them as monsters. The protagonists of the Turner Diaries are identifiable in-text as people with foresight who are doing the things that must be done, hard things perhaps but fundamentally good things.
I imagine you could generate readings of The Sum of All Fears that would identify it as a pro-nuclear terrorism book. After coming across some anti-trans people who decided to read the TNG episode "The Outcast" as telling the story of a confused person from an advanced genderless society who was properly brought back into alignment with what was right, so saving her from a predatory Riker, I realized that you can read something anyway if you really want to. The pro-nuclear terrorism reading of Clancy may be possible, but it would be recognizable as forced to everyone save the people invested in that reading for whatever reason.
I also read both novels.
Hence my observations that The Turner Diaries are so horribly poorly written that they would only "convince" someone who already believes all that crap in the first place. So I think it is very doubtful that the phenomenon of "Normal Person reads TTD = Normal Person regresses Rabid White Supremacist" occurs, which is implicit in this case.
As for Tom Clancy, what I saw was your average novel that would be used as an action movie script: evil bad guys being evil because that's what evil bad guys do.
What I tried was simply to apply here the same "logic" that would be followed in the first case.
The assumption in the first case (which as I've already developed I think is quite ridiculous and nobody would believe such a silly theory) is that everybody would buy "Barkashov plagiarized TTD", nobody would for a moment consider "hey, this is too stupid". are you sure we're not being fooled?", and you'd get massive, angry mobs searching houses and rounding up random people to lynch to death anyone in possession of a copy of TTD.
So, following that same logic, you get that there would be rabid mobs looking to lynch to death anyone who owns a Tom Clancy novel, organizing burnings of Tom Clancy novels, and of course repeated attempts to assassinate Tom Clancy...
...that is, if all the Abbreviated Agencies not coming down on him to basically use every possible legal trick to ensure Clancy has to sit in the electric chair.
It is true that said like that it sounds tremendously stupid, forced and crazy, but that is exactly the point. Show with a similar example how crazy the idea that someone just read a book and did something crazy like 4/10 would look to the average viewer.