As the first reply mentions, mIRC and IRC are basically two different things. mIRC allows one to access IRC and lets the user see the chatroom via the GUI.
RE: The politics of IRC, IRC isn't meant to be and has never been a democratic process. Failure to accept this will reduce your ability to enjoy what IRC does usually offer. IRC is in most cases an invitiation for people to connect to someone's computer and therefore the owner of that computer (and their appointed staff, if any) are basically the surpreme commanders, though many try to not portray that image, including me.
This basically means that each owner has the right to determine who gets to connect to their computer, which in itself is not unreasonable, it's no different to a landlord deciding who is allowed to enter their house. The said owner also gets to set what conditions apply to those allowed to connect. For the life of me I don't understand why someone's sexual preference should be a consideration as this cannot be determined on the internet without uses volunteering their personal details, that said, the owner still has the right to restrict access to whoever they like, based on religion, colour, political persuasion, sex/transgender/preference, the country they come from, whether they have weird hairstyles/colours, 50 earrings, is married to a yowie and any other petty reason they see fit. My view is that none of the above are worthy reasons to restrict people, but there are people that arn't as understanding as I, and alot of other people, are.
The good news is that there are hundreds of other servers that will accept people from all walks of life. Run through your mIRC server/network listing or visit sites like http://irc.netsplit.de/
which log network activity and just pick one at random.
In finishing, while I said that it's a server owners right to make their own choices, it's also their loss if they make a bad choice.