They are givening out incorrect information if that is what you were told or read.
Effectiveness of Condoms
Condoms are classified as medical devices and are regulated by the Food and Drug Administration (FDA). Condom manufacturers in the United States test each latex condom for defects, including holes, before it is packaged. The proper and consistent use of latex or polyurethane (a type of plastic) condoms when engaging in sexual intercourse—vaginal, anal, or oral—can greatly reduce a person’s risk of acquiring or transmitting sexually transmitted diseases, including HIV infection.
There are many different types and brands of condoms available—however, only latex or polyurethane condoms provide a highly effective mechanical barrier to HIV. In laboratories, viruses occasionally have been shown to pass through natural membrane ("skin" or lambskin) condoms, which may contain natural pores and are therefore not recommended for disease prevention (they are documented to be effective for contraception). Women may wish to consider using the female condom when a male condom cannot be used.
http://www.cdc.gov/condomeffectiveness/latex.htm
Sexually Transmitted Diseases, Including HIV Infection, Latex condoms, when used consistently and correctly, are highly effective in preventing the sexual transmission of HIV, the virus that causes AIDS. In addition, consistent and correct use of latex condoms reduces the risk of other sexually transmitted diseases (STDs), including diseases transmitted by genital secretions, and to a lesser degree, genital ulcer diseases. Condom use may reduce the risk for genital human papillomavirus (HPV) infection and HPV-associated diseases, e.g., genital warts and cervical cancer.
Laboratory studies have demonstrated that latex condoms provide an essentially impermeable barrier to particles the size of STD pathogens.
People say on forums and Yahoo Answers that condom doesn't 100% protect against HIV even when the latex doesnt break. They say it happens because HIV cell is smaller than latex layers or something
the use of latex, polyurethane or polyisoprene condoms will protect you from contracting hiv.
And where did you hear about that? Condom is designed and made to protect you from any Sexually transmitted disses / Virus. If condom fails, it breaks catastrophically and see your penis barely expose.