Even if McCartney did offend the current President, Obama acted the only way he could. It is not his job to call out his guest of honour, especially in such an occasion. Did you honestly expect the President to embarrass Sir Paul McCartney? There is no way to rectify such a situation, so the President was forced to accept the artist's comments.
Also, Gilvary thinks that Obama admires McCartney because neither of them were born in the United States. That logic is severely flawed in two ways: Obama was born in the United States, and foreigners don't necessarily sympathize. Especially coming from a grown adult, claiming that Obama was born outside the United States is the most ridiculous thing I ever heard. Oh by the way, the Tea Party also told me that McCartney was born in Kenya. Second, strangers don't connect based on what they are not, they connect through common trait.
Obama admires McCartney because he was a prominent member of the most famous band in history. End of story. And as far as the "Taxman" goes, taxes have not gone up for 95% of families under Obama.
Gilvary also tries to provide a British equivalent, which is as flawed as her argument. If Michael Jackson were to be knighted by Queen Elizabeth, he would need a time machine to travel to the late 1500's. I think you mean Queen Elizabeth II. Good thing the Bulletin didn't publish this one.
Even more egregious than Sir McCartney getting the prestigious Gershwin Prize because of illicit drug use is having George Bush elected to the prestigious President of the United States position after illicit drug use. Oh wait ... he didn't actually win.