No, that's pretty normal for moderate people to say or believe but of course if you always attack them by claiming they're extremists, they aren't going talk to you about it are they?
The scale thing is irrelevant because the morality of it isn't related to scale. It's just a consequence of larger populations at the time and bigger differences in tech levels. It's clear from history that the Barbary pirates etc weren't saying to themselves, well this much slavery is ok, but that much would be immoral so we won't do it. They were just a few centuries earlier when there were far fewer people around.
The scale thing is irrelevant because the morality of it isn't related to scale. It's just a consequence of larger populations at the time and bigger differences in tech levels. It's clear from history that the Barbary pirates etc weren't saying to themselves, well this much slavery is ok, but that much would be immoral so we won't do it. They were just a few centuries earlier when there were far fewer people around.