The question is, "Why is it so acceptable for women to objectify men?".
Well, who cares about fairness. Between peoples, there is no fairness. Life is inherently unfair that way.
But life is fair in this way: what you sew you will reap.
Let's look at who is being objectified:
The Tall Dark and Handsome man - a lot of girls want him. In turn, he has the opportunity to sleep with lots of girls. If you're dating him, you better watch out. If things aren't going so well, there's always going to be some other girl waiting in the wings ready to fuck him, and most people given the temptation won't be able to resist. Especially a man with that much opportunity.
The Wealthy man - lots of girls want him (and his money). He's figured out that not only can pussy be rented for an hour at a time, but he can also buy the love of some girls. In fact, if you're with him, chances are he'll be tempted to buy the love of a younger girl when you become old (and ugly). Why would he do it? Because money is power, and most men can't resist the temptation to exercise it. Besides, he felt powerful when he won you over with money, and it'll be an opportunity to feel that very same way again with a younger chick.
The Beautiful Blonde girl with the Big Tits - lots of guys want her. But she's crass and shallow. Why? Because she knows she can snap the neck of guys just by walking down the street. If you're dating her, watch out. She'll have trouble resisting that feeling of being wanted by someone else, as soon as your relationship hits mildly rocky times. Why not? It was so easy to pick you up with her beauty, why not pick up a new one when things get a little tough?
The Fresh Young Pretty girl who's a bit Naive - lots of guys want her. Why? Cuz they're sick and tired of having to deal with a woman their own age, who has real needs and makes real demands of him as any mature woman would. But if you decide to date that pretty young thing, watch out. She'll realize you're old and as soon as she finds a younger one to match your wealth, she won't mind trading in your experience for his youth, excitement, and better body.
The thing is, who cares about those who are doing the objectifying? If you objectify, you're attracted to the very same shallow qualities everybody else is attracted to, so you're really no further ahead. In the end, if all you appreciate is those things, you're not appreciating the things that could bring you real happiness. The one doing the objectifying is the one who will miss out on a lot. That is reaping what you sew.