What percentage of young MSM have HIV?

Recently, a fuss arose over a quote regarding HIV and young men who have sex with men (MSM) from Regina Griggs in a OneNewsNow article regarding youth and sexual identity. She said (in context):

Research shows that individuals often go through periods of gender and sexual confusion as they grow from children to teenagers to adults. Griggs wonders why, then, would schools opt to send children along a dangerous path. “Why are we allowing people to tell them, ‘Try it — you might like it?’ Over 70 percent of young kids 13- to 24-years-old, men having sex with men, are now HIV-positive,” Griggs notes. (see editor’s note)

Griggs here is describing prevalence, which is the total number of people in a population with a certain disease at a given time. However, this is clearly incorrect, as other bloggers have pointed out.
She may have been referring to a fact sheet at the CDC called HIV/AIDS Among Men Who Have Sex with Men when she was quoted by ONN.

In the United States, HIV infection and AIDS have had a tremendous effect on men who have sex with men (MSM). MSM accounted for 71% of all HIV infections among male adults and adolescents in 2005 (based on data from 33 states with long-term, confidential name-based HIV reporting), even though only about 5% to 7% of male adults and adolescents in the United States identify themselves as MSM.

The ONN editors recently added a note pointing out the 71% figure from the CDC fact sheet.
This simply says that men having sex with men accounted for 71% of infections among all males reporting infections in 2005. MSM was a large driver of infections reported in 2005. While this is a sobering statistic, it does not mean what Mrs. Griggs said it means.
I do not know what the actual prevalence of MSM aged 13-24 with HIV is but it would need to be over 800,000 cases in order for her statistic to be true. This does not seem possible.
I arrived at that number by looking US Census data for 2005 which pegged the number of males in the US between 15-24 at about 19.7 million. The CDC estimates 5-7% of this age group as being MSM which yields 1.2 million males. If 70% of this group was HIV positive, then that would mean Mrs. Griggs is claiming that about 840,000 young men have HIV. Of course, these numbers are estimates since I rounded figures and used the Census data starting with age 15 and not 13 as the CDC does.
According to the CDC fact sheet, there are not that many people living with AIDS at present:

At the end of 2005, an estimated 217,323 MSM (191,362 MSM and 25,961 MSM who inject drugs) were living with AIDS, representing 67% of male adults and adolescents living with AIDS and 52% of all people living with AIDS.

These numbers are staggering enough without exaggeration or misinterpretation. I commented here because many have asked about the validity of these numbers and the quote made me curious about the scope of the issue.