I resent the racial connection you are making. Age is an issue with leaders. Color of skin is not. Age affects mental sharpness, physical stamina, physical fitness, likelihood of serving out a term, and more.
If Paul were the nominee I can already see the TV clips showing Obama playing basketball, playing softball, playing golf, shirtless at the beach, going jogging, etc. The subliminal inferences will not be lost on the American public.
Age is an issue...which is why we have a VP. Its one thing to say, "You need to make sure we have continuation of government." It is another to say, "Because you are not young and pretty, you are ineligible for office."