To remove personal details in log messages, you can use git filter-branch with the --msg-filter flag.
--msg-filter <command>
       This is the filter for rewriting the commit messages. The argument
       is evaluated in the shell with the original commit message on
       standard input; its standard output is used as the new commit
       message.
PS: The email address that you have in your public profile in Github ( https://github.com/account ) is only revealed to people visiting your profile. The email address that you use in your commits ( https://github.com/account/email ) which and used to identify your commits is not revealed to public