Except we are not talking about toddlers, it's a small and vocal part of the Mileena fanbase that is not representative of its entirety. If Scorpion was left out, people would harass them, and that would apply to any popular character because we're talking about some uneducated people that are gonna be uneducated no matter what. I don't think the correct reasoning would be to leave Scorpion out because "the fans don't behave".I think they might have meant "validate" more than "justify" but it makes perfect sense.
If you had a toddler, and they wanted something they couldn't have or didn't need, would you give in to them after they threw a tantrum? No, you wouldn't because you'd be setting a precedent. You'd be telling them that you'd always give in as long as they threw big enough of a fit.
NRS shouldn't give into the tantrum-throwing toddlers we call the internet. If they did give them Mileena, they'd just be harassing NRS for the next character. Then the next, and so on.
I'm all for giving NRS creative space, it's clear they didn't intend to include Mileena, and that's probably as it should be. But excluding characters because of the behavior of some fans doesn't make sense to me. I like Mileena and I'd like to see her in a future game, and I don't want to be represented by people that harass developers.