As it happens, there has been a similar, though slightly less dramatic, shift, in the attitudes of 30- to 49-year-olds. In 1992, 27% of women and 23% of men in this age group described themselves as "strongly pro-life"; in 2006, 38% and 34%, respectively. For "strongly pro-choice," the proportions declined from 38% to 26% of women and 34% to 21% of men.
The 30- to 49-year-old cohort in 2006 includes those who were 18 to 29 in 1992, so one may surmise that this group has moved in the "pro-life" direction. This would be consistent with the self-interest hypothesis: As young adults age, they tend to get married, and therefore to become less worried about unplanned pregnancy.
I do not completely discount this possibility, but I think he is missing out on another important piece. The older we get, the more conservative we tend to become. There are a variety of reasons for this. part of it is self-interest, but part is also that we have seen some goofy liberal attempts at fixing things (including things that are not broken), and they often just don't work.
Also, the older I get, the more valuable life seems to me.
So I do not think that this is just self-interest, I think there is a practical and spiritual component here.
The interesting question is whether, over time, this same right-shift phenomenon will affect aging younger populations who currently seem to favor normalization of homo-erotic activity.