But you have to be prudent when making public health policy. Oral transmission is an extremely rare event, probably because of the inactivation of virus by saliva. You are not at risk with passive oral sex. The active partner is at some risk. It is more risky to swallow semen.
Oral sex is probably safe prior to climax.
You have to use a rubber for oral sex. We drive a car every day. The risk of death from being killed in an auto accident, even if wearing a seat belt is far greater than the risk of getting AIDS from someone not in a high risk group. Some people may decide to walk everywhere instead of drive a car. Some people may decide to even further reduce the low risk of AIDS by using condoms, dental dams etc.