While that may be what the Catechism says, the reality is generally much different. Calling someone's feelings, which they have no control over, inherently sinful (and offering absolutely no outlet for them) isolates them and leads to feelings of hopelessness - I don't think that's very respectful or compassionate. If you're straight, your lust is still called sinful, but you at least have the option of marrying. Someone who is gay can't do that - at least not within the Church.
More to the point though, if your "solution" to the problem is just to ban gay people from the priesthood, that presents a real problem: how do you identify who is gay? Ultimately, that relies on people being truthful, and I definitely don't see someone who is entering the priesthood with predatory intent being truthful about their sexuality. The people most likely to be honest about their feelings and desires are, paradoxically, the least likely to offend. Better to address the cultural issues that promote silence and isolation for young gay men, making them easier victims.