Oofta, these are two different things.
He didn't say anyone's doing it to "get their jollies murdering evil children", he's saying that having an entire race be evil is a convenient justification for killing the kids without feeling guilty about it. Not that they're LOOKING FOR opportunities to kill kids. More that, if the scenario puts kids in the way, they don't want to have to wrestle with a moral dilemma and wind up feeling guilty. This is not entirely unfounded. It's exactly what Gary Gygax was saying with his "nits make lice" reference to Chivington in 2005 (link below).
In my opinion what Gary was talking about was an easy/lazy way out of dealing with situations like he presents players with in the Caves of Chaos in B2. He gives you a bunch of humanoid antagonists, and in his nod to Gygaxian Realism, the lairs include a bunch of noncombatant women and children. In real play groups can choose to deal with this numerous ways. DMs can choose to elide the kids. DMs can run the women also as combatants, or rule that they are peaceable and ask for truce, swear to leave the area, etc. OR, in the "nits make lice" approach, players can just exterminate the vermin and be reassured that the creatures were never capable of peaceful negotiation or growing up to be nice and non-threatening adults, so the players don't have to feel guilty or worry about their characters no longer being Lawful Good.