Can someone help me verbalise why I found this and other, similar things he says, offensive? It's just disdainful, no? Aimed at showing me up as stupid and small? That's what it feels like, anyway.
He claims he was genuinely asking whether or not I was serious (about some utterly minor point about numbers) but it's the tone of voice, isn't it?
Things were going so well. I think he spoiled it by using this negative, unhelpful, slightly contemptuous phrase - he thinks I spoiled things by calling him out on it 