Sweat contains a large amount of pheromones which have been proven to attract the opposite sex. So in a way yes antiperspirant deodorant can make men less masculine. Body odor is another thing and no one likes that. I read somewhere that the musty smell under our arms comes from nervous sweating as opposed to active sweat. The nervous sweat is what stinks.
I do not think body odor can be described as masculine (or feminine for that matter)! Odor is an offensive smell no matter what sex you happen to be. Anyone who feels it is not a problem should try working or living in close quarters with someone who suffers from it.
There is nothing masculine or even attractive about body odor. People need to control their odor and deodorant is a great way to do that. I really don't want to go around having to smell sweaty, stinky men all the time. It may be natural for a person's body to smell that way, but there is a solution to the smell that should be used.
Women who want to get close to men should not have to worry about how they smell. Smelling bad is not very attractive. That is true for whether a person is a man or a woman. It is better to be polite and deal with body odor so that it does not offend others.
Deodorant is an unnatural product for a healthy, normal man to use. The scent of a man in perfect health should theoretically smell masculine and pleasant. It should be naturally alluring to a female of the same species. However, the artificiality of modern modes of living and the disgustingly horrible nutrition habits of most modern men cause them to require equally unnatural products to cover up the resulting odor.