If they were actually on the site in question and commenting about those former Presidents, then there might actually be something to be offended by if your a lefty. Except this is none of that, they are not members and they did not post anything to the so-called “right-wing” site.
But it helps plant the meme that ‘right wing’ sites are evil hives of scum, villainy and bad words. One little step at a time....