Was Henry VIII’s Annulment Refused on Political Grounds Alone?

This is a common Protestant (especially Anglican) claim. I have a few problems with it: 

1. Although I see it regularly asserted, I have never seen anyone prove (or even seriously try to prove) that it’s true. Seemingly, the burden of proof should be on the person alleging that the pope was acting with evil (or at least political) intent, but this is never done. 
2. Henry VIII’s case is a particularly extreme one. Under canon law at the time, you couldn’t be married to your brother’s widow. Catherine was very briefly married to Prince Arthur (Henry’s brother), who died five months after the wedding. Catherine swore, and there’s every reason to believe she was telling the truth, that they had never consummated the marriage. And so Henry sought, and received, a papal dispensation to marry Catherine. That’s why it was particularly galling when Henry then went back to the pope demanding to have an annulment granted on the very issue, he’d received a dispensation previously. Henry was showing himself to be two-faced, and for Pope Clement VII to annul the marriage, he would have to contradict his predecessor Pope Julius II’s dispensation. 
3. Additionally, even if it was true that popes were guided by politics rather than love of God or concern for the sacrament of marriage (which, again, I don’t think Protestants ever bother proving), that doesn’t change things. Henry shouldn’t have been able to get an annulment from his marriage to Catherine. So, whether the pope’s intentions were pure or not, his action (refusing to grant an annulment) is the one that’s clearly in keeping with the vision of marriage presented by Jesus Christ.

Ultimately, Henry VIII’s serial philandering and successive marriages are a gross violation of Christ’s teaching about marriage. His behavior is utterly indefensible. And so, instead of actually defending it, certain Protestants just point the finger at the pope instead. I don’t think that’s a very convincing diversion.