No, it is not Professor Dershowitz' age, or not just his age. He has had many clients but the one client of his heart is the state of Israel. This "proud" Hillary Clinton voter has been compromised by a greater interest:

"...Alan M. Dershowitz, a Harvard Law School professor emeritus who has advised the Trump team on Middle Eastern policy."

https://mobile.nytimes.com/2017/06/09/us/politics/trump-comey.html?_r=0&referer=https://www.google.com/