Why are sex predators bad?

Ethical sex should be:

• Responsible. This means you should know about sexually transmitted diseases, the causes and prevention of pregnancy, the emotional consequences of sex, etc.
• Consensual. Both parties should be willing participants with the right to say "no" at any point. (By law, underage people cannot give consent.) And no deceptions, no seductions.
• Equitable. Both parties should feel that they're getting what they want out of the encounter.

Sexual predators violate all three of these conditions.