I hate to use a feminist argument, but rape/molestation isn't about sex. It's about power (and with molestation the abuse of trust).
Saying "boys want it" or "penetration is different from being penetrated" is bullshit. You think there aren't just as many girls, if not more, who fantasize about being with older men in exactly the same way? Because there are. Hell, I bet you there isn't a teen or preteen girl out there who hasn't gotten off to the idea of an older guy fucking her brains out.
Would you argue that older men molesting younger women is okay then? Clearly it's their fantasy, they want it, should be alright, yeah?
Stop being a hypocrite. I'd it's bad for one, it's bad for all. I'd it's good for one, it's good for all. I don't care what you pick, but don't be a meely mouthed hypocrite about it insisting it's okay to "rape" boys when it's bad to do to girls.