(CBS NEWS) -- It's not a lot to ask - Sen. John McCain, R-Ariz., just wants everyone to "lighten up" and enjoy his joke about Iran's president being a monkey.

Responding to reports that Iranian President Mahmoud Ahmadinejad is ready and willing to suit up his astronaut gear to help his country reach its goal of achieving a manned space flight, the notoriously candid McCain wrote on Twitter Monday morning:

"So Ahmadinejad wants to be first Iranian in space - wasn't he just there last week? 'Iran launches monkey into space' http://news.yahoo.com/iran-launches-monkey-space-showing-missile-progress-003037176.html"

Having evidently faced some backlash for his shot at the leader of a nation testing long-range ballistic missiles with very sad-looking animals, McCain later followed up on the social media site: "Re: Iran space tweet - lighten up folks, can't everyone take a joke?"

But despite the plea, McCain-the-cutup isn't making any friends with his material, even on the right. Rep. Justin Amash, R-Mich. - an Arab-American - responded on Twitter:

"Maybe you should wisen up & not make racist jokes. @SenJohnMcCain: Re: Iran space tweet - lighten up folks, can't everyone take a joke?"

For the record, it's not McCain's first stab at comedy: Two weeks ago, he made a crack about "waterboarding" Secretary of State John Kerry in his Senate confirmation hearing.