You're not seeing things clearly. You need to understand that statistics do not tell you anything about individuals. Also, you cannot use a stat to predict whether someone is going to have syphilis or AIDS or any other disease for that matter.
The best insurance for the prevention of VD transmission is a clean bill of health. If a bisexual male has a clean bill of health, there is no reason why he should be treated differently from a straight male when seeking employment in the straight porn industry.