I'm not eliminating the idea he wasn't shown sexual material, or wasn't exposed to innapropriate touching. I'm just saying we can not say that conclusively.
http://www.atsa.com/children-sexual-behavior-problems
It looks like there was at least some inappropriate exposure:
The following is taken from Patsy's 1998 interview at
http://www.acandyrose.com/1998BPD-Patsy-Interview-Complete.htm
7 TRIP DeMUTH: A couple of questions
8 Tom. With Evan Colby, was there ever a time
9 when Burke and Evan were under the porch without
10 their clothes on something, like that?
11 PATSY RAMSEY: (Nodding).
12 TRIP DeMUTH: Can you tell me about
13 that?
14 PATSY RAMSEY: Well, I think
15 Cynthia Savage, my housekeeper-nanny, told me
16 about that one time. They were, there isn't a
17 porch to be under, but I think Evan taught Burke
18 that it was easier to go pee-pee outside than to
19 take the time to go inside to go pee-pee, so he
20 sort of taught him how to go behind the tree.
21 Evan is a little guy.
22 TRIP DeMUTH: How little is little
23 Evan?
24 PATSY RAMSEY: Well, I want to say
25 Burke was probably six or seven, Evan was 7 or
0120
1 8, or something like that. And Suzanne told me
2 she came out and saw -- I think she said they
3 were kind of by where we kept this trash can,
4 sort on the left side of the garage and Evan had
5 his pants down showing Burke his -- works.