Did he mention any other current partners? If not, then now you know why that is.
I've never had to address this on a first date , or not being someone who goes on dates, i should amend that to "so soon after meeting someone". And even then, the worst thing i had to do was tell the person to wash their feet (or their butt, in one or two cases).
I guess i would appreciate being told about my breath, same as i wouldn't want to walk around with a booger or with the seam of my pants split and no one let me know. On the other hand, maybe the guy has a mental illness.
Cue lectures about me being a small-minded douche-bag for saying that.