I will give you this, the risks are not equal. Sucking cock is riskier than licking pussy. The two idiots who told you that crock are,well, idiots.
http://sfsi.org/fellatio/ the excerpt below is taken from the link
While fellatio (cock sucking) is more risky than cunnilingus (pussy licking), it is less risky than unprotected vaginal sex, and much less risky than unprotected rimming or anal sex. Things you can catch from performing fellatio include clamydia, herpes, gonorrhea, syphilis, and HIV. Things you can do to reduce YOUR risks for giving head:
Check your partner’s genital area for lesions or sores. Although someone can still carry a sexually transmitted disease (STD) and show no symptoms, your risks are much higher if there are any open sores.
Don’t brush or floss an hour before giving oral sex. Brushing and flossing increases your risk of transmission of several types of STDs for about an hour due to gum irritation.
Don’t take semen into your mouth. Some STDs (including HIV, the virus that causes AIDS) are present in semen of men who carry the virus.
Use a barrier. For instance, you can try one of the unlubricated condoms on the market. There are also mint flavored unlubricated condoms available.
You might want to send this to the morons who think pussy is a raging cesspool.