Totally not batty. You will probably find Tony Benn to have been one of the rare politicians who was utterly respected by all parties. He was immensely intelligent who was steadfast in his beliefs, he outwitted other politicians with his deep knowledge and floored many of them (in the politiest) during any discussion.
He was deeply deeply anti the Iraq war and never towed the party line over it, he stood up and fought for the people. His death is not a suprise, he has been ill for many years and divested by the loss of his wife. I was so lucky to have seen him speak at the LSE many years ago, it was a total privilege to hear and see him, one Ill never forget.
Any tribute you hear about him today will be genuine, from any party.
I do find it odd that you described him as batty, I get the feeling that you have confused him with someone else?