What do you think of people who insist on saying “AN historic”?

I know (at least I believe) that, for example,

“… Scott Brown and I reached an historic agreement…”

is correct, and that

“… Scott Brown and I reached a historic agreement …”

would be incorrect.

But I can’t help hearing it as “snooty” and “smarty pants”.

I know, it’s my problem 🙂