That’s exactly why.
To disavow someone you have to be responsible for them in some manner. Cheney was not responsible for Larry ... Wilkerson was Powell’s staffer, along with Armitage... and later hooked up with Sanders, who is no friend of Cheney’s, either, while Powell threw his lot in with Obama, biggest opponent of all. Wilkerson was also tied in with birther Pat Lang of the wacko LaRouche group VIPS, which was feeding conspiracy crap to Ted Kennedy, and was working hard to counter Cheney and Rumsfeld as well. You don’t need to disavow your enemies or other people’s staffers- the fact that they’re enemies working for your main opponent is distance by default.