Why does he do that?

I’m seeing this guy and it’s been going well. The only thing that irritates me is that when I’m unable to do something like meet him on a certain day when he’s free and I’m busy or unavoidably late he gets a bit stroppy and texts stuff like ‘don’t bother’ or ‘never mind’. I know it’s over text so tone gets lost but it puts me off sometimes. Is this a red flag or am I thinking too much?