wrote a lengthy reply, but shortly: Yes it is bad, I would never even think of it, Turkey suffers a lot from it on eastern parts of the country (child brides being forced to marry their cousins etc), but I don't want to directly say it is bad, because while it is bad, that's less likely to be helpful towards solving the issue.
(another reason is, you never know if someone here was subjected to such a thing, forcibly or not, deceptively or voluntarily, and I would rather not have someone get depressed over my statements)