If that's true, can men welcome a woman not being so aggressive if you wish to have the roles switched? For example, just going up to a man, introducing themselves and asking them to dinner. Why can't we do this without seeming needy to a guy on the onset? Why does that emasculate you so much? I suppose it's a power struggle then.

Double standards suck. Some characteristics of a female aren't all that bad. The good ones like being up front and honest about what's going on. Comes more naturally to a woman than a men.

I would say the naturally occurring reaction to the mans mental calculus based on his experiencing her physical representation where the main sense offering information being sight is the main reason for a mans initial interest and what motivates him to start a progressing dialogue.

But is not the sole motivator for continued interest and has only a little influence on whether or not he bonds with her.

"Why can't we do this without seeming needy to a guy on the onset? Why does that emasculate you so much?"
When a guy is attracted enough to you it compels him to be friendly, and nice, and chase you, to come up to you and talk to you, to ask you out, to be closer to you, to eventually go for physical contact.

If a guy isn't coming up to you to talk to you and ask you out then he is either not attracted to you, or too insecure to follow his natural reaction.

Which means they are going to come up with some reason to blame you for their problems, their lack of attraction, and/or to validate their insecurity.
Voila you're needy and emasculating them.

It's not really a double standard.

It has more to do with how male and female brains react differently to the chemicals that naturally occur when presented with someone of the opposite sex than anything else.

"being up front and honest about what's going on. Comes more naturally to a woman than a men."
That's the only double standard you've really brought up.
When men are upfront and honest about what's going on with their emotional reactions they are called dogs and pigs.
Women are forgiven for being the weaker and more emotional sex.

When one group is castigated when they are more up front and honest, they have greater incentive to come up with ways to prevent being upfront and honest.