The difference is eugenics involved forced sterilization against your will, where what people here seem to be calling for is a free voluntary sterilization option.

I think the lines are very blurred in reality. Doctors and social services didn't always sterilize by force. Many times it was a matter of convincing a person, or outright tricking them.

Just the threat applied today of the government taking away your children unless you can provide a minimum standard for them, is enough to convince many people to not procreate. Ie eugenics with a different process.

If you read the above paragraph and think "what's wrong with that", then you're in company with a lot of people who are not unreasonable. But it springs from the same idea as eugenics. Now consider the above paragraph applied to minorities or the indigenous population. Suddenly it is an awful thing.

You can also argue that nobody should have the right to pass on hereditary diseases and conditions to a child. What do you do if they want to do it anyway? Etc, etc. There are arguments for and against. Well being of the child vs human rights of the parent.