Flew was an atheist for more than fifty years when his health was in his prime. An 85 year old man has better than a 50% chance of suffering from some form of mental impairment. Dawkins doesn't claim that Flew is senile, he just suggests it is possible. He was right.
Hm. Thanks for the diagnostic tool.
Now, when you stop spouting foolishness and start talking sense in however many years, we'll know you're senile, too.