I don't disagree with what you're saying, but my take on Seymour is that he's not meant to be cultured or particularly intelligent. I take him as an example of someone who, having achieved a certain level of success and wealth, decides that means he must always have been smart and sophisticated and that he deserves everything he wants. So he starts spouting an easy, surface-level ideology which may sound fancy or literate. But underneath it's all a matter of might makes right and he with the most toys wins. And for Seymour "the most toys" seems to include people, which I would argue is potentially very threatening. He does come off as cartoonish. But his wealth and his ego are, unfortunately, all too real. If he were only obsessed with Lena, that would be creepy. But he seems to be growing as interested in Ian as well, just in a less sexual way. And even Axel, who has plenty of ego and a controlling personality, basically becomes a yes-man in front of Seymour.