First and foremost, let's get this out of the way:
A person's "Sexual Preference" is defined by who they are attracted to, not by which nerve endings they stimulate. In other words, neither doing it for yourself nor allowing someone else to put something inside of your bottom is going to make a heterosexual male turn into a homosexual one.
I say this because so many males resist the idea of placing anything "in there" - vibrator, butt plug, or even an Aneros or other brand of prostate stimulator/massager. They resist as if the mere thought of doing so might turn them into homosexuals, which it seems is an extremely scary idea to many men. Preposterous! No amount of stimulation to your anal nerve endings should challenge your sense of self identity of being a heterosexual. And it certainly will not change you into anything you aren't already!
There are almost as many "erogenous zone" style nerve endings in the anus as there are in the female clitoris. Added to those are the bundled nerve clusters that are the male's equivalent to the female G-spot, that in men are instead positioned to exist nearby their prostate gland. These are nerve clusters which hold the potential for males for full-body and multiple orgasms, just as the G-spot does for females (that's why the man's prostate is often called the "male G-spot" - sometimes called the "P-spot" for that nerve cluster's position being so near the prostate).
Whether or not you can muster a full-body "P-spot" orgasm (a whole blog in itself!), the fact that problems like prostitis, enlarged prostate, prostate infections and prostate-cancer are on the rise in this country has become a factor that pretty much mandates that men take some kind of approach towards prostate health, like perhaps using the Aneros MGX or other prostate self-massagers on the market today. In our "sit-down society", not nearly enough fresh oxygen and nutrient-rich blood is being delivered to the lower abdomen, particularly the prostate area. I predict these "toys" from Aneros (originally developed as medical devices to provide the needed massage to the prostate region in order to increase circulation) will soon become prevalent as today's men respond too-late to their own personal prostate-related crisis'. Avoid the problem up front by helping fresh blood and oxygen to get to that area using these "toys". I say, better an ounce of prevention, eh?! And such a pleasurable way to stay healthy! (Read more on male sexual health, including some useful exercises, here and here!)
Lastly, the pure sexual enjoyment to be received from those nerve endings surrounding the sphincter and deeper within the anus is something any woman who has learned to relax her own second sphincter (as males will have to learn) has come to appreciate. Probably as a result, there is a growing interest by women in strap-on play with their male partners, and this is encouraging men to allow such experimentation more than ever before. (Just as with females, anal play for men requires some considerations for safety and to avoid bruising the second sphincter, as detailed in my other blog on anal play for beginners.)
So, men, get over it. Anal play will not change your sexual preference, it will simply give you more fun and enjoyment. Prostate massage using a sex toy will help to improve your overall sexual health, and possibly will extend your lifetime. Harness play is a ton of fun, and lots of women love doing it - or would like to! So, relax that butt of yours -- you'll be glad you finally did!