Most Helpful Guy
It sounds like he found an excuse to pick a fight with you and it probably relates to the underlying reason for why he was on a bad mood. The reason may concern your relationship but it could be unrelated.
You need to talk with him to find out what is below the surface. What you don't want is another argument. To guard against that, why don't you invite him to meet you somewhere for lunch? You will have fewer arguments when you meet in a public venue and fewer arguments when you meet during the daytime.