That sometimes people are stupid and deserve to reap the consequences of their actions, even if they were being deceived.
Physically, a man has complete control over his reproductive potential. He can abstain, he can have non-vaginal intercourse, he can use a condom, he can withdraw, he can use a spermicidal lubricant. If he decides not to use one or more of these five methods to control his own reproduction, then he is basically ceding control to chance and the goodwill of other people. He is not taking responsibility, and therefore he has little grounds for complaint when things don't turn out as he wishes they would. "Oh, but she lied to me!" doesn't cut it, because she was only in the position of power because he put her there. He had control and he gave it up, willingly.