I am disturbed by the large amount of intolerance displayed in this thread, but it isn't the kind of intolerance most people are talking about in this thread. Having the opinion that MtF transexuals are men and not women is a valid opinion. Just as having the opinion that they are women or a third gender is a valid opinion. Attacking someone who holds the opinion that they are men as intolerant or bigotted is not ok. That is intolerance. The only tolerance that really matters at the end of the day is tolerating opinions and beliefs you disagree with. There is nothing difficult or noble about being tolerant of things you agree with, identify with, sympathize with, or don't have any general disagreement with. It is being tolerant of the things you disagree with strongly that is the true tolerance that allows society to become a better place. A great many words have been spent arguing that gender is different than sex and that gender is a social construct. It is worth noting that this argument itself is a social construct. A person can agree with that opinion and a person can also disagree with it and hold the opinion that gender is intrinsically linked to biology and sexual reproduction. If a person has that opinion they are not hateful or discriminatory towards trans people. If a person is attracted to women, and does not consider MtF transexuals as women, then they have every right to be upset if they were to find themselves in a situation where they had had a sexual relationship with a MtF transexual who had not disclosed that fact. If a person feels that way they are not discriminatory, bigoted, hateful, or tranmysogynistic (or however that word that was just made up is spelled).
For this very reason I would say it is extremely immorral and disrespectful for a trans person to have a romantic relationship with another person, especially if it is sexual in nature, without disclosing that they are trans to them. To do so is not respecting the other persons opinions and beliefs and trying and force their opinion, that they are women, onto them. Enough people hold that opinion that it is a reasonable assumption to make that there is a good chance that the person may not be ok with it and the trans person should disclose first so that their partner can make a fully informed decision. I could understand how a trans person could be upset by other people disagreeing with them and believing that they are not the gender they identify as but it is for each person to decide their own opinion on the matter. A trans person does not get to disregard someone else's opinions. Being upset, even very very upset, gives no one any authority, moral or otherewise, to dictate the opinions and beliefs that other people have or how other people should feel about something. Respect and tolerance is a two way street. If trans people, or those being offended on their behalf, want other people to respect and tolerate their opinions and beliefs then trans people have to respect and tolerate the opinions and beliefs of other people.