Why cast someone as Richard Dawkins????

Initially when Kamal explains Pooja that Dawkins has come to his house...My mind immediately flashed "Richard Dawkins" and 2 seconds he reiterates "Richard Dawkins"

I thought since both Richard Dawkins and Kamal Haasan are both strong atheists who never let go of a chance to ridicule religion,maybe Dawkins made a guest appearance..But what I saw somone pretending to be Dawkins

As the movie progressed further,I was questioning,why did they make a world famous evolutionary biologist look like a MI6 agent??? cant they have chosen another name???