If it were, then it would.
But typewriters had proportional fonts as far back as the 1940s. And there's no evidence of any kerning. Those are simply closely-spaced typewriter strikes. And they're uneven. A typewriter with sophisticated kerning wouldn't produce randomly-uneven text.
According to Steve, IBM didn’t produce a typewriter with proportional fonts until 1966. Is it plausible that the BC was typed on some other brand of typewriter that had proportional fonts? I guess it must be, since we see the same proportional font on the Nordyke twins’ BC. If it’s legit on their BC, then it must be legit on Obama’s too.
And I think you’re right about the kerning. When you look through the whole document you see misalignments in the characters that are very typical of what you get with a manual typewriter. Occasionally you’ll see what looks like a kerned pair, but just as often you’ll see a pair where the spacing is wider than normal and in some cases it’s a vertical misalignment. So to me the kerning argument goes out the window too.
So I’m back to thinking the conspiracy theory doesn’t hold water.