In fact, the evidence, from "non-friendly" sources, people who refer to all intergenerational sexual activities as "abuse", indicates just the opposite:

Numbers are specifically for boys' short-term reactions to sex with adults:

Finkelhor, D. (1979). Sexually Victimized Children. Free Press, New York.

Positive & Neutral = 62%

Fromuth, M.E., and Burkhart, B.R. (1987). Sexual victimization among college men: Definitional and methodological issues. Violence Victims 2, pp. 241-253

Positive = 53%, Neutral = 30%

Goldman, R.J., and Goldman, J.D.G. (1988). The prevalence and nature of child sexual abuse in Australia. Australian J. of Sex Marr. Fam. 9, pp. 94-106.

Positive = 39%, Neutral = 32%

O'Neil, M.R. (1990). Puerto Rican and New England college students' reports of childhood sexual abuse and sexual experience. Dissertation Abstracts International 52, UMI No. 9110201.

Positive = 41%

Predieri, K.A. (1991). Long term effects of male child sexual abuse. Dissertation Abstracts International 53, UMI No. 9208876.

Did not feel victimized at all = 48%

Schultz, L.G. and Jones, P. (1983). Sexual abuse of children: Issues for social service and health professionals. Child Welfare 62, pp. 99-108.

Positive = 68%, Neutral = 24%

Urquiza, A.J. (1988). The effects of childhood sexual abuse in an adult male population. Dissertation Abstracts International 50, 356B, UMI No. 8906961.

Positive = 38%, Neutral = 26%

(source for the numbers: pp. 115-116 of Bauserman, R. and Rind, B. (April 1997). Psychological Correlates of Male Child and Adolescent Sexual Experiences with Adults: A Review of the Nonclinical Literature. Archives of Sexual Behavior 26, pp. 105-141. An abstract is available.

Long-term reactions were less pronounced, in general.