That is actually not such an unreasonable assumption. Yes there are groups like Pink P who help arm and train LGBT folks. But someone who is LGBT is much more likely to be on the liberal side of things, urban rather than rural, and thus less exposure to civilian gun ownership.

There is also a lot of stigma among liberals. I have heard from a number of LGBT folks that it was far easier to come out to their Republican friends as gay than their Democratic friends as owning a gun- Republicans disapprove of gay people a lot less than Democrats disapprove of gun owners.