Signorile's blunt response: no. Unlike Bill Clinton, the "first black president" dethroned by an actual black president, President Obama did not grow up "immersed" in the projected culture he allegedly represents.
Here's more from his explanation at The Huffington Post:
…The "first gay president" label just doesn't work, no matter what rhetorical device you employ. And it makes us gays seem silly and starved for validation.
Bill Clinton grew up poor and among the African-American community, including in the churches in which he worshiped.
Barack Obama didn't grow up immersed in gay culture or understanding the gay experience, and he had no such connection to the gay community… For almost four years the president, for political reasons, didn't say he was for marriage equality. Then, after being pressured by gays, and after many in his own administration couldn't hold back their own support for marriage equality, the president announced his support in the midst of an election campaign.
Though Signorile certainly thinks we should tip our hats to the commander-in-chief, and that he deserves "immense credit," the "first gay president" moniker should be reserved for a actual gay person.