Sometimes the mere presence of one word or small phrase is enough to make me approve of a song.

This one had 'rickets' and 'yak milk' in close proximity.

Strongly approve.

Surely in African-American Vernacular English "be" is a habitual or occasional marker, which in the context of the song would imply that McCain is sometimes old, but sometimes not old?

lulz

Obama is Facebook, McCain is Friendster! Haaaaaaaaaaahahahaha!

Surely in African-American Vernacular English "be" is a habitual or occasional marker, which in the context of the song would imply that McCain is sometimes old, but sometimes not old?

No. When the verb "be" is inserted into the sentence, it emphasizes the permanent or ongoing nature of the condition - it's an intensifier. It doesn't mean only for right now - it means for an extended period of time, or even permanent. So when someone asks where your mother is, you could say "She home," meaning she's home right now. Or you could say "She be home," meaning she is home most of the time.

McCain be old.

Thanks Miko!

Omg, that's hysterical, i didn't see TE's comment until just now.
And i beg to differ with on the 'be.'
Sometimes you just be.
Verbs of being, is, was, am, be
Be is all verbs of being.
"He be tripping" means he's tripping.
"He be tripping." means that dude is seriously fucked.
"He BE tripping." means he will be tripping or quite simply fucked.
"HE be tripping." means that guy is quite confused or possibly presiding under a misconception.
*giggle*

That was genuinely funny. "He was at Moses's BRIS!"

From the course notes to this I have:

C. Grammar. Black English has systematic grammatical differences from
Standard English.
1. To be. In places, Black English is simpler: She my sister is good
Black English.

2. Habitual "be." Elsewhere, Black English comes out ahead. To say
She be walkin’ to the store does not mean that she is doing it right
now but that she does it on a regular basis. Standard English
usually leaves this difference to context: to indicate regularity,
Standard English uses the bare present--She walks to the store.

So, it confused me until Miko explained it: it seemed to me it should simply be "McCain old".

i hope that didn't come off as rude, or to be making a joke at anyone's expense.
i just thought the idea that sometimes he was not old was really funny. And that be was always an intensifier. And explaining slang with slang just was me amusing myself.