Here is another email I received about where the term MSM originated:
When the term MSM was coined it was to created it as you described to create an objective term so that materials produced could be relevant to any man who has sex with other men, regardless of how he identifies -- in getting information to men, and wanting it to be relevant they wanted to remove any internal barriers that might allow a man to say -- this isn't about me.
And if you think about it -- the exact reasons why homosexual sounds so right to you -- "a term with a history and culture" -- means that it runs into the same issue when using the term gay or bisexual -- by appearing to a segment of MSM as not being applicable to them.
Its also important to note that MSM is a clinical term and isn't really designed to be an identity, its just a way of putting a set of behaviors under a single roof that might be applicable to a variety of identities.
Currently those within the bisexual community are pushing to also make HIV/AIDS materials that are an expansion of the MSM materials that include behaviors MSMW -- so this carries information about sexuality transmitted diseases that men can carry with little or no effect that has a larger effect on women; additional information as relates to bisexual health and awareness, etc.
The Boston community is really in forefront of a lot of this work here in the US -- Fenway Community Health has been producing a specific bisexual targeted HIV/AIDS program that produces pamphlets specifically stating bisexual and another one for MSMW -- you should check them out. You should also look at the Bisexual Resource Center's website as they have a multitude of resources on Bisexual Health as well as other categories.