A Google image search for gay cumshot indicates there are 37.8 million results. Cumshot -gay has 44 million. If these numbers are correct, then gay and non-gay cumshots are almost equally common online, and it's a toss-up (pun intended) as to which we should use. 

There are really two separate issues here. 

One is that Wikipedia illustrates sexual and pornographic practices that most educational sources would not. For example, I have yet to find a medical website that illustrates its article on ejaculation with an ejaculation video, or a printed encyclopedia that shows a photograph of ejaculation. So while Wikipedia usually says that due weight should derive from practices in reliable sources, in this particular case Wikipedia departs very sharply from practices in reliable sources, because it understands WP:NOTCENSORED to override WP:NPOV. In other words, it assumes that reliable sources are censored, and that Wikipedia is not. 

That is not my understanding of policy, nor is it the understanding of policy as written, where WP:NPOV / WP:DUE is the senior and WP:NOTCENSORED is the junior policy, but in practice, WP:NOTCENSORED tends to win out over WP:NPOV and WP:DUE because of our demographics. So that is our status quo. 

The other issue is that Wikipedia in practice IS censored by not illustrating any of the articles on pornographic terms of art that apply to both gay and straight porn genres with images taken from gay porn, even though, as we can see, both are published in almost equal numbers. One reason is that User:Seedfeeder, the artist who drew most of these images, is straight and usually declined requests to draw gay images (he has done one or two, but it isn't what he enjoys doing).

http://commons.wikimedia.org/wiki/Special:ListFiles/Seedfeeder

I did once convert one of Seedfeeder's images (of snowballing) so the recipient of the semen was a male, rather than a female, because that was actually what the sourced text was calling for. And I confess it did give me a certain satisfaction to see male users complain that the image was disgusting, and demanding that it show the woman receiving. So far, however, no woman has complained. 

The German article still has it wrong by the way, as it confounds snowballing with cum swapping; they are different activities. Snowballing originates in gay sex and is when the (male or female) recipient spits the semen back into the donor's mouth after oral sex. Cum swapping is primarily a pornographic practice, where one woman spits the semen into another woman's mouth; it never touches a man's lips. 

Andreas