If a man shows up to a tech conference dressed like the guys from Jersey Shore, he's going to be looked down on by everyone there. He'll be assumed to be part of the delivery people doing setup for the booths.
If he complains that he's a programmer and that he shouldn't be judged by his clothing, he will get mixed results.
It's true that if he turns out to be a nice guy, and a great programmer, then people will change their opinions of him.
But the one thing we cannot do is demand that the entire world see signals differently than they see them out on the street.
When someone dresses like the men on Jersey Shore, they do so because they are signaling certain things. They're signaling masculine power. Strength. Sexual prowess. Fighting ability. Etc.
Women who dress extremely femininely and girlishly are also sending signals that literally BILLIONS of people already know how to receive.
Don't be surprised when people interpret signals the way that is most beneficial to them in 99.9% of cases.
This is not a message that men from New Jersey or Women in general cannot be seen as programmers. It's a message that signaling matters, and we must be aware of what messages we're intentionally sending to others that we may need to overcome.