I hope I can address some of your points to your satisfaction.
Ideally this site is meant to address and give specific advice to parents (or those people acting in the temporary role of parents) with problems that they actually face. Some hypothetical questions that may help parents facing such problems are also on-topic, as are questions from children over 13 years of age having problems with their parents, and a few other kinds of questions as well.
While wanting to raise awareness about important problems is admirable, that particular goal doesn't always fit this site's guidelines set out in the help pages and the sites Meta. Questions such as Are ExerSaucers/walkers/jumpers bad for children or is that simply a misconception? and How should the children be taught to be wary of physically present strangers? are on topic, but your question was not about specific dangers children might face. It was asking for a statistic:
What percent of kids who, under 8 were exposed to sexual abuse do NOT go on to become perpetrators when they are older? Is there any evidence to support that the rate is above 10%?
While that may be very important, it's not on topic for this site. It's not asking about a problem parents face; it's asking for studies to confirm an experience you've had:
I have my own personal observations that suggest that it is around 12% (ish) do NOT go on to abuse others, and I am looking to be disproved.
Your question was not down voted and closed because no one cares about child abuse or because it was "politically incorrect". It was closed simply because it is not on topic for the site.
There is a site on Stack Exchange where (if you show a source in the media), you might get such a question answered. That is Skeptics.SE. However, since they require a source (not just an observation), your question could not be migrated there.
How can I ask questions meant to empower me as a parent, and provide a forum for educating other parents about child abuse prevention if it is immediately and unilaterally down-voted?
We want to empower parents. I'm not exactly sure how knowing this particular statistic can help individual parents with their children. Most parents don't know the background of every person that comes into contact with their children, so while it might be relevant on a case-by-case basis, even there, it's unlikely to fit on this site. For example, a question asking, "My brother was sexually abused as a child. Is it safe to let him babysit my children?" might be partially answered by such a statistic, but statistics don't address that particular situation (statistics are only statistics), and the answers are going to be primarily opinion based*, which is also a close reason.
*primarily opinion-based — Many good questions generate some degree of opinion based on expert experience, but answers to this question will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise.
For additional reading:
What types of questions should I avoid asking?
“Actual problems that you face”
What topics can I ask about here?