Pretty sure I mentioned it earlier, but... again. While the internet stuff did have some influence, it was only some. The thing about /pol/ is that by and large (so far as I'm aware, anyway, as I don't actually spend much time browsing it), most of the shit they spew is either explicitly coming out of non-net media already (and has been longer than the internet has had pictures) or cheerfully in line with it, sometimes fairly promptly looping back into it.
Think a fair amount of the hubbub on that front is that folks in more built up areas, or more connected to internet and its goings on, and so on, are significantly overestimating their effect (just due to how much more the internet et al is part of their lives) and severely underestimating what was already circulating around. People not around it with some degree of regularity don't seem to realize exactly how virulent talk radio (and the other offline venues for "information" propagation) is, and has been for decades. The horn tooting on their end probably adds to it, too, but any influence the online alt-right et al had was piggybacking pretty hard on the infrastructure (for lack of a better word at the moment) that was already there.
Basically, you don't really need to take them seriously until the internet finishes really sinking into our nation, and finishes strangling out TV, radio, and so on. Still a ways to go, on that front, particularly with regards to likely voters (and/or people with notable political influence).