I like several of the answers already given. I think MichaelK's answer is probably sufficient. But I had a couple additional points.
Forced anything implies some entity to do the forcing, and some entity besides the person being forced to make the choice. Putting that choice outside the individual means that there is an entity in society that is prior to the individual. Assigning the ability to enforce the choice means that entity has the ability to make vital choices about the individual and enforce them. Any such entity would have vast potential for harm, in at least equal measure to the degree of good it could possibly produce. We should take great care before we permit any such entity to exist. We should make extreme effort to be sure we want that power and authority in society before we consent to it.
But this is something for which it is extremely difficult to be sure we actually are correct in such choices. (Even supposing that this entity acts with best interests of society as the goal, never becoming corrupt, never acting for vindictive or petty or ambitious or insane reasons.)
Should we seek to eliminate, for example, the gene for sickle cell anemia? The reason this gene exists is (if I recall correctly) it provides some degree of resistance to malaria when the individual has the gene from only one parent. If we remove this gene then maybe everybody in the tropics dies of malaria in the next generation.
How can we be confident that any given change to our genetics is in fact preferable? Maybe in a very few cases we can be confident that certain genes can be safely dispensed with. Possibly hemophilia. Possibly some other genetic diseases, such as things that cause people to die at age 12 or the like.
But if we start messing with genetics, how can we be sure that any given change is in fact desirable? Is it really the case that a genetic predisposition to obsessive compulsion should be eliminated? How about addictive behavior? How about the tendency to "zone out" when the environment is a bit dull and repetitive?
I think there's a huge possibility that we would wind up enforcing some person's (or some small group's) whims and bigotry. Oh, this person's too fat, too skinny, can't do math well enough, can't do enough push-ups, whatever, off to the sterilizatorium he goes. Oh no! He's the kind of person who drives ALL the way to the end of the on-ramp then dives into traffic! Ahhhh! No gonads for YOU!
From an entirely other aspect: It's quite likely that we will very presently be able to control which genes an adult passes to children. Even be able to make corrections of a few genetic flaws. So hemophilia should be entirely detectable in carriers, and could be eliminated from progeny. And not too expensively. So we could move over to tech that won't require sterilization of anybody, but will still achieve nearly the same proposed benefits. At present the tech only allows one gene to be modified, and only in very limited ways. But technological advances in this area do seem to be advancing rapidly. Probably in 10 years we should be able to dial up what we want in children.
That will be something that needs a lot of careful thought. Maybe we want to dial up a few really smart kids and let them think it through.