That's because the people who think objectification of women is bad tend to also think objectification of men is bad. Those people don't want to live in a world of ubiquitous or or even just balanced objectification; they want to live in a world with none.
Even if it is natural, that doesn't mean it's desireable. That's just an appeal to nature.
While laws are an extreme method, they're routinely used to better ourselves, and even more often to better others. It's worked for (what we currently consider) undesireable behaviours like theft, smoking in public places, environmental pollution, seatbelt wearing, illegal parking, murder, and looking funny at cops. That's a pretty varied list, so why wouldn't it work for sexual objectification? I don't think we should use such a drastic approach, but it's not ridiculous, either.
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* Cowardly assuming we're all in the West.
Both. There's still a lot of latent homophobia throughout the US. What I mean by that is that there are many folks who are decidedly pro-gay-rights, but still feel uncomfortable around the sexualization of the male gender.
There's one thing I'm interested in: happiness. What's going to make the most people happy? Many laws that are morally prescriptivist, like those banning gay marriage, end up just oppressing people because it turns out gay marriage is perfectly fine and doesn't harm anyone.
I don't believe open displays of sexuality are harmful to anyone so long as we don't have double standards and we do exercise good judgment. So the idea of outright banning them by law does indeed seem completely ridiculous to me. It's just as ridiculous to me as banning gay marriage or banning porn or banning prostitution.
The reason we do have double standards is precisely because we've been led to believe over generations that the sexualization of men is wrong. Because many men haven't learned to be comfortable with their own gender, homophobia has been able to flourish for decades. It's gross when two guys kiss, right? Of course it is--you can find millions of people who will agree with you because they've carefully been hidden from that their entire life. Banning sexualization and sexual objectification will just lead to future generations who are even more incapable of coping with the realities of human sexuality in ways that aren't immensely harmful to many people.