I see two main questions: Is it a new phenomenon, and aren't they just homosexual.
The answer in both cases is no.
You say transexuals are homosexuals
Who says that transsexuals are homosexuals? I sure don't.
then why can't a transexual just be homosexual?
Why can't a [enter kind of person here] just be homosexual? [cue standard answer] Because they're not!
Why do you presume people who are transsexual are seen as homosexual before transition? I'm wasn't. Before and during transition my attraction is to men, the difference is others now perceive me as in a gay relationship, if my transition had anything whatsoever to do with sexuality I would not transition and I would live a happy non-interesting existence in straightville. Problem is I'm not a female, doctors thought I was when I was born, parents were sure I was growing up, they even fitted me out with an appropriate wardrobe full of dresses and other girly things, but my core identity is now and has always been male (earliest memories are about 6 years old). Doctors have given me a medical option whereby I can bring my mind and body into synch.
Let's put this in perspective: By transitioning I risk losing anyone and everyone in my life who may have a moral issue with my medical condition, I risk unemployment, I risk never being able to find a partner who will accept me physically, I risk discrimination and even the threat of physical harm. I risk it all. The payoff that makes this necessary for me is peace of mind, of feeling whole, of looking in the mirror and seeing who I am on the inside reflected outwardly. I can live, or I can exist. Given a choice who would pick the latter?
Why do the have to make the switch? It's almost like a form of self expression like tattoos or peircings but instead you chop off your dick and replace it with a vagina. I don't understand.
What do you place more importance on, your mind or your body? Think about someone severally mentally retarded, then think about someone who is paraplegic. Whose core being is more whole.
If you're male picture yourself in an intimate relationship where you have no dick, if you're female picture yourself having one. It's a disturbing thought really, to have every aspect of your relationship change because your partner is determined not only based on what you're attracted to but what they are. What makes more sense a transwoman who dates men to have a dick and date gay men or to transition and date straight men?
As much as I enjoy tats and piercings I sure have no interest in risking losing everything in the name of self-expression, and do not be mistaken I do not do it for relationships, I do it for survival.
Like I said, I'm incredibly ignorant about it. Transexuals might be the only minority I have an intolerance for, and I feel like it's because I'm uninformed.
That does not make sense, you state that you're incredibly ignorant about transsexuality, but then you say you have intolerance for it. If you're ignorant isn't the better default position neutrality? Why negatively judge something which you do not understand?
Didcha know that they can see parts of transsexuals brains that match closer to the gender they identify with? I expect it's a matter of time before it's seen as a form of intersex.
is it just a new mental illness that doctors have stopped viewing from a medical perspective and allowed to become circus freaks for emotional happiness?
I don't view myself as a circus freak, why must you? It's not like you can tell I'm trans just by looking at me. I look rather normal and average thanqueverymuch.
In all honestly you would never have changed genders a century ago because it was impossible. So transexuals never existed, only homosexuals.
Transgendered individuals in time gone by did not have the medical advances now available to transition but they did certainly exist, in just about every culture.
Here's a list from non-western cultures which will give you an idea of that, so no they are not new concepts, they are however often people who were accepted by their society before western missionaries and civilisation came knocking and proclaimed they should be shunned. There are some lovely stories of how the Native American Two-Spirit people were targeted despite often having unique and important roles in their tribes simply because the soldiers were affronted by them.
Akava'ine (Cook Islands)
Two-Spirit (North America)
Bacch