I have had the opportunity to go through BMQ and further courses with people of a broad variety of beliefs and orientations. I will definetly echo the previous posters, and add this to it:
I know of 3 members who were open about their orientation at BMQ. 2 graduated, and one VRed for separate reasons. In my short and limited experience, as long as the person in question is not making an effort to impose on others to the point where it becomes a reverse-harrassment situation, there really is no difference between a member who is happily married in a hetero relationship as there is to someone who is enjoying a same-sex relationship.
I am proud to serve with ANYONE who decides to serve their country, and who decides, as I did, that their gender, orientation, or cultural background did not and does not influence their decisions.
Having interacted with LGBT people, both in and and out of the Forces, the only advice I can give to someone in this situation is that they don't allow anyone to use it as a prejudice against their ability to do the job, but they don't use it as an excuse if someone is giving them the gears for NOT being able to do a job. The excuse of "Are you jacking me up because I'm gay?" is NOT ON. Your supervisor is giving you the what-for for being a pump, not because you are gay. As long as you can do the job, whatever you do in the privacy of your personal life should be of no consequence to anyone else.