One issue is: what is the physical mechanism by which some knowledge (like people's personalities) is created and maintained? Is it caused by genes? By education? By a mix of both? Is the knowledge stored in the form of ideas just like the my idea that South Park is a good TV show? Is it still stored in the genes in adults? Or in the brain but in a different way than my TV preferences?
The second issue is: how possible is it to change this knowledge? Is it hard or easy or impossible? Can it be changed just like a TV preference, or more like learning physics, or not at all? Is it a choice, or just something that happens to people which they bear no responsibility for? Or are their parents morally responsible?
Almost everyone on both sides of the debate believes the following:
1) If the nature side is the correct answer to the first issue, that means the answer to the second issue is that it's very hard or impossible to change, not a choice, and parents are not responsible.
2) If the nurture side is correct about the first issue, that means the answer to the second issue is that it's easy to change, people are a blank slate and can choose to be whatever they want at their whim. (Or like that but somewhat milder.)
That's why whenever I tell people that personality is ideas, autism is ideas, sexual orientation is ideas ... nurture is absolutely correct WRT the first issue ... they reply by telling me that they don't have control over those aspects of their life, and don't believe they ever did.
I think if issue two wasn't at stake, people wouldn't really care about issue one. What does it matter where the knowledge is, and the detailed mechanisms of how it gets there? What most people care about is the affect on their lives, and what it means in terms of moral responsibility.
The funny thing is they have it backwards. Nature traits are far easier to change than nurture traits, because genes have less knowledge than memes, and the requirement to change a trait is basically to create more knowledge than whatever is making you the way you are now.
But even if they didn't have it backwards, conflating the issues is senseless. And so is assuming that what traits can be changed, and how, is obvious based on the first issue. In fact how to change knowledge is a hard issue to analyze! Epistemologers know the answer in outline (conjectures and refutations; piecemeal gradual changes; respect for existing knowledge; optimism; rationality; error correction; etc), but working out specific, practical consequences for real life situations is often difficult. Very few contributors to the nature/nurture debate know that outline at all -- they are completely out of their depth, and often don't even know that epistemology is the key field -- yet they still take a large portion of the answer for granted and consider it so obvious it doesn't need serious analysis.