"Strong opinions, weakly held" sounds right to me.
I couldn't care less how confidently somebody holds an opinion.
I think the word "strength" here should signify a battle-hardened opinion that has won out over others in a practical or theoretical sense. Strongly-supported...?
That's not to say that that it's wrong to be confident in the opinions you hold, but if you want to have strongly-supported opinions you can't protect them from being tested against other opinions. Let them win on their own merit...
"Strong opinions, weakly held" http://www.codinghorror.com/blog/2008/05/strong-opinions-wea... http://bobsutton.typepad.com/my_weblog/2006/07/strong_opinio...
"I aim to fight as if I am right, and listen as if I am wrong" http://blogs.hbr.org/sutton/2010/08/its_up_to_you_to_start_a...