Im going to go out on a limb here and say no I dont think having children is a right, its a privalidge that some such as drug addicts and abbuser dont deserve.
I would even go so far as to say in my own little "in my head ideal world" I think classes on parenting before your allowed to have a child would save so much heartache down the line.
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I see what you're saying about classes, they do have some classes for moms who have been identified by Social Care as needing extra support. However, id parenting classes were compulsory, who would decide what would be on the curriculum. It goes back to that scenario of one person/one body deciding on behalf of the entire population what is best for children.
I agree, there could be standardized info disseminated, eg, instead of giving out Bounty packs with loads of freebies, they could put in a copy of material that would apply across the board for all babies, eg, issues on love, attachment, bonding, and not just for babyhood but as your child grows. Instead they give out free pamphlets on things which quite frankly (to me at least) are not anywhere near as useful when it comes down to the issue of parenting.
Also, if you enforced lessons, then parenting stops being instinctive, which is what parenting should be. People will be taught to distrust their instincts and parent in line with the curriculum.
Also, I think child abusers only become child abusers once they have the children. So it would be impossible to determine whether or not they would become one until they had a child. Child abusers tend to be offspring of child abusers, and some will continue the cycle of abuse, whilst others will parent totally differently, its not easy to predict, so you can't really restrict the right iykwim?