I'd talk to my *** about it, and my reaction would depend on what they said, and how they think and feel about what they're doing and how they're handling it. Ultimately it's gong to depend entirely upon them as it's their life, their body, their decision. Hopefully any major decisions they've made in their lives they've thought through and are approaching rationally, maturely and on their own terms.
I think I'd be more concerned if they were going to pursue a career in the military, where these days they might very well find themselves blown up or shot to death somewhere in the Middle East. Yet you'd probably see a lot of people suggesting that they'd be proud of their ******** for making the decision to serve their country. Interesting that I imagine a lot of people would rather see their ******** in a position where they could be maimed or ******, or could end up maiming or ******* another, rather than having sex. I'm not sure what that says about society, but it's probably not something good...