The Doctor is deeply silent, because the word genocide makes his stomach twist. There's a silent look of that they're not too different in some ways.

"I hate it when the world ends like that." The Doctor remarks dryly, "I'm so, so, sorry for your loses."

"Really. Memory wiping too. All sorts of bad in these universes. But I assume that the memory wiping can't be permanent, surely if it could be resolved with science."

A short pause, "Is that what you do? Hop around between dimensions?"