With prolonged exposure almost anything is possible.
For example, there are files on sites like Pornhub and Spankbang that combine images of sexy girls with images of male penises. They flash the images of the girls for a split second then a cock then a girl. Now this is 'obvious' and most truly straight guys will stop stroking to the sexy girls and thus not get turned gay.
However, if you take the concept a step further and make the male body / cocks last too short for the conscious mind to perceive but long enough that it does register you can theoretically turn a 100% straight guy into at the very least a bisexual.
Now once you have linked the response to sexy girls to also register for male bodies and cocks comes the next step of turning a guy. At this time you would slowly add extra "aversion" imagery (such as guns, snakes, spiders, piles of feces, etc.) to appear during the same frames as some of the girl pictures, while the cock pictures would include positive imagery (like ice cream, money, etc.) this would with enough exposure make a person naturally more responsive to the male bodies in porn than female, at that point just straight porn followed by a program designed to make the person be increasingly turned on by male bodies would do the rest gradually.
… Alternatively you could just use the quick and dirty shortcuts that SB uses and hope for the same results.