Pervert is the wrong word

To want to give things to attractive people is a natural impulse which I expect is very common. A perversion would be a twist on a normal thing, like only tipping ugly people, or chastising attractive people.

That said, I think your friend was right to criticize you. Unfortunately we suffer from a lack of vocabulary. 'Pervert' is one of those emotional words people throw around when they're grasping for an insult. What she should have said is 'horny biased sucker' or something like that.

Basically, servants should be tipped based on service, including things like speed, accuracy, hygiene, and manners. Tipping them based on their attractiveness or how lewdly they dress is inappropriate.

It may be okay to a degree, however. For example, I find slim people to be more pleasant servers because it conducts an appropriate atmosphere. Incredibly obese people are anti-hygenic and would lessen a dining experience. However, that is a separate issue from attractiveness, and includes all extra bulk (like large breasts too) or with hair.

Another thing is that it's the exact opposite with clothing, the more the server wears, the less likely their skin flakes are going to fall onto your food, so that's a good thing. Tipping a girl for unbutton her shirt so boob cells can land in your macaroni is incredibly ungentlemanlilike. You need to look at the bigger picture. Yes: she brightened your day, and probably some other men's, but she just as likely made it a bad day for a bunch of jealous women, all who are part of society that you will interact with.

Boobs really aren't something to be 'proud' of, so I'm not sure why you term it that way. It's not like you work to grow them like muscle. You can be proud of your skin if you take care of it I guess, but you can easily advertise that with the face or arms, doing it with cleavage too is excess.