Strictly speaking, those two statements are not in logical contradiction. Even if the sins are less serious (relative to other types of sins) ... in his opinion ... it doesn't mean that most people couldn't end up going to hell as a result of them. Even if less serious, it might be that they're the easiest to fall into and hardest to get out of.
Of course, Bergoglio is an idiot ... in addition to being a heretic. There's no such thing as a sin that's purely of the flesh. Sin consists of an act of the will and the intellect. If something happens ONLY in the flesh, then it's not a sin. What Bergoglio is TRYING to say, I think, maybe?, only God knows, is that people often fall into these from weakness rather than malice, and they are therefore in that regard often less displeasing to God than sins done from malice. But the level of malice could be higher for a sin of the flesh also, so the mere fact that it's a sin of the flesh isn't of the essence in terms of what pleases or displeases God.