I have serious doubts about zero’s citizenship, but the language chosen by his mother to express an idea is not strong proof at all. In fact, it’s no proof. People use language rather loosely and, because zero’s dad was from Kenya, and because many people defer to their spouse, using the word “return” to Kenya may well have been phrased that way in deference to him.
I think this “evidence” is wishful thinking on the part of the person presenting the information.
Taken this by itself is not enough evidence, however, the shear accumulation of all the evidence seen as a whole makes a compelling argument that Obama was born in Kenya. From Michelle Obama who said that Kenya is his home country to the Kenyan Minister of Lands Orengo who said explicitly that Obama was born in Kenya.