The right wing characterization is also cartoonish. It's on purpose. I could have said "extreme" instead of "pure" and perhaps you would not have objected.
As for lack of diversity, there are left wingers out there who'd agree with my characterization, so long as I'd give the mice blank/identical brains as newborns, but diverse physical characteristics. The idea is not that the mice stay the same forever. The idea is that left wingers tend to believe that we're all born with very blank and malleable brains, and that despite this, we become diverse as adults, because we grow up in different circumstances. For a left winger, this is a positive message, because it means that anyone can become anything if they just put their mind to it.
The right winger will tend to believe that "once a bad seed, always a bad seed", and will, for example, be in favor of death sentences, because he thinks it's not possible to change people. The left winger sees a prison sentence in a completely different light, as an opportunity for reform, because of his unwavering belief in people's ability to change for the better.
You see it in the education system too. The left winger will want to design an inclusive education system where everyone gets the same treatment, to give everyone a chance to blossom. The right winger might see this as oppressive, because it doesn't give the best performers a chance to excel, as every kid is dragged down to the lowest common denominator. He never saw the children as having equal potential to begin with, so why have the naturally smart kids waste time together with the rest?
See, what I'm describing is a purified logically consistent version of the two wings. Hardly any real person is this logically consistent, and will draw a line somewhere, instead of pursuing their ideology to its logical conclusion. The logical end point of each wing is crazy, which is why most people never go that far. But why favor any particular side? There's no reason to. I can't be a right winger without taking it to the extreme, because my logic will take me there, not can I be a left winger without taking it to the extreme, so I stay in the middle.
I grew up in a Scandinavian social democracy, with Labor Party parents, so I know the left wing point of view very well: We're all the same on the inside. It's merely circumstances that make us different, so we all deserve to have the same things, and (if you extend that line of thinking a bit) we thus all have the ability to do anything, given the right nurturing. That, and nothing else, is what the cloned lab mice are meant to symbolize.
Perhaps there are cultural differences that are causing some friction here, then. Here in the US, the problem with the education system is that the funding mechanism for schools relies on property taxes. Affluent areas have well funded schools and schools in impoverished areas languish. The issue with education isn't whether or not students who have shown aptitude are allowed to flourish, it's whether children are able to achieve their potential to the extent of their abilities. There is a hard limit to what can be achieved by children from poor communities, while the children of the wealthy are nearly guaranteed success regardless of their individual talents. Add to the mix the racism that plagues our society...
So left wing approaches to education here attempt to mitigate the problems that come from inequality that actually prevent intelligent and talented individuals from achieving excellence. The same social factors allow mediocrity to achieve stellar results, due to inherited advantages.
Again, I think this is a very silly misinterpretation of leftist thought. People are born with a wide range of mental and physical characteristics and abilities. Both nature and nurture influence human development. Left wing thought will urge us to value people equally and give them equal standing in society, despite varying abilities. It's a matter of social equity.
There are enough people, mostly on the left wing, who refuse to accept that we are born with different brains, that author Steven Pinker felt he had to write a book called The Blank Slate to refute this idea. In a famous example of blank slate thinking, a sex change clinic for children with ambiguous genitals here in Norway would randomly assign sexes to children, believing them to adapt to any sex assigned to them, since gender roles were obviously a construct of society, and male and female brains were of course identical at birth. It turned out to be disasterous for the children in question, and they changed their practices to include a gender identity test.
The way the Scandinavian system is designed is strongly biased toward this kind of thinking.
I should note that what Americans tend to call leftism isn't very leftist compared to what we have here in Scandinavia. Obama would not be considered a leftist, and even the populist right wingers in Scandinavia approve of universal healthcare, for example.
Based on what you've said so far, you're closer to a centrist/moderate than a left winger, on my scale, which probably extends much further left than any sensible American would reasonably want to be. Basically, the European (and especially the Scandinavian) scale of leftism begins where yours ends.
You can't please the gender rights faction of your leftist movement without accepting that genetics is completely insignificant, because if you do say it makes a difference, you might be taken to be a sexist, and perhaps even a bit of a racist, since different ethnicities have somewhat different genes. And once you do that, you must apply the same principle everywhere to remain logically consistent. And that's how you get the cloned mice.
I really don't know what to say about your statements about gender and race. They're really not applicable to my own experience with movements in my country.
Of course Obama is not a leftist. Far from it. His version of universal health care was a plan hatched by right wing think tanks and first implemented by a Republican governor.
I'm absolutely not a centrist, by any stretch of the imagination. I am an autonomist Marxist.