Does anyone know why Santorum's "Chain" Remark, isn't being used to defend Biden?

My friend posts on a Forum with both Democrats and Republicans. Of course the topic of Biden's chain remark came up and Republicans were falling over themselves posting insults about Joe.

Then a Democrat came on and posted a link at TPM which included a statement of Santorum's made in August 2011 in Iowa...here is what it said:

"The Romney campaign is sounding the alarm over some hyperbolic language Vice President Joe Biden used on the trail — language that Republicans have also used"

"Rick Santorum invoked chains last summer to warn Iowa voters that health care reform would lull citizens into government dependency. “They will put you in chains called ‘Obamacare,’ and you will never break away,” Santorum said"

Link to Article here: http://2012.talkingpointsmemo.com/2012/08/romney-biden-obama-chains.php The article also discusses the use of the word "unshackeled" By Boehner & Romney.

Now my friend said once that was posted, Republicans didn't know what to say. They had no comeback. They were asked several times what the difference was between Santorum and Biden's statement and why they weren't offended by Santorum and the use of a "code word". No replies.

I am mystified as to why Santorum's statement isn't being used by Dems to defend Biden. It certainly shut Republicans up immediately in that Forum.

When my friend sent me the link, I thought good, it's over with. Instead there are still jabs at Biden. How can republicans be "offended" by a term used by one of their own and why aren't Dems pointing that out?

Anyone know? It certainly would seem to put an end to it all. Thanks.

** I've cross posted this in General Discussion, because I'd really like an answer to this. If that is not allowed, I apologize and respectfully ask the Moderators to remove this post from this Forum. Thank you!