Can we be honest? In the dominate circumstance of daily hetrosexual experience, women are checking out men, men are checking out women and both are somewhat primal, objectifications based on instinctive checklists buried in our genes. For those in the fluid gender pools the checking out is wide open and perhaps still rooted in genetics. The male gaze attack is just a rhetorical ruse to control circumstances. Now one can be rude with a stare but on average the whole thing takes about 5 seconds those that fail the check list get no more attention. Sadly for the PC crowd nature is and will remain stronger than their biased thinly veiled ploys to undermine natural behaviors!

You missed the fundamental part of Male Gaze Theory, which is that media content is created in a manner that presupposes the audience to be cis-het-males.
Frankly, a simple Google/Wiki search would have informed you of that.

So the point is : MOST cis-het-males PREFER to see hot and sexy girls THEREFORE, most media content has sexy hot girls.

I'd say that this part is mostly true, in that males do prefer to see sexy hot girls.
However, the theory has a major flaw, in that it doesn't really analyze what other identities like to see in their media.
It could be argued women do also enjoy to see sexy hot girls, which obviously makes their display an optimal marketing solution.

Everyone objectifies everyone else. When you know nothing about them you have no choice but to categorise them according to their most obvious attributes in order to determine how to act toward, or about them. Only later, when and if you get to know them as an individual can you begin to treat them as an individual. You objectify your boss as a boss instead of a person. You objectify your taxi-driver as a taxi driver, not a person. You objectify your mother as a mother-figure rather than an individual personality, because that's how the brain works.

Is sexism inherently wrong?

I took a film class where I was introduced to the "Male Gaze" which he eventually added the caveat of the Male Gays (where he played us an example using Silence of the Lambs to prove transphobia in Hollywood). I think most advertisers are seeking the male viewership but I've always been told that women are the biggest shoppers and that advertisers are aware of this and hence attempt to attract the female gaze as well, in magazines etc. Movies might be more male-centric which is a reflection of the hierarchies we are always failing to climb to the top of so we need motivation to, guess, what, attract the Female Gaze!

Your attempt at answering your own question was actually pretty good and I tend to agree. I do not think it is valid. I like your follow up question where you asked, don't women also objectify men but in their own means. Yes they do, in my opinion. Men do tend to look at women in a sexual nature, and it is often (if not damn near always) that men will look first to physical attractiveness. Where women will objectify men by looking at them through a social lense, their social status, their economic status, etc. Of course there are always exceptions on both sides. So, if men objectify women by sizing them up physically and imagining what it would be like to sleep with this particular woman, then women objectify men by sizing them up to their social and economic status and imagining what this particular man might be like as a father.

No validity to that theory, as there is a natural explanation, and you stated such quite clearly.