Where did he do that? You have a quote?
Greenspan says ARMs might be better deal
http://www.usatoday.com/money/economy/fed/2004-02-23-greenspan-debt_x.htm
Fed chief pushing ARMs
http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2004/03/02/BUG275BONF1.DTL
http://themessthatgreenspanmade.blogspot.com/2007/10/alan-greenspan-on-arms-in-2004.html
Remarks by Chairman Alan Greenspan (actual speech text, referenced item is just before his conclusion)
http://www.federalreserve.gov/boarddocs/speeches/2004/20040223/default.htm
Do a search, you will find all kinds of articles for and against this when it first came out, I just picked some of the first ones to come up.
You also have to take into consideration that they, the FED, was signaling before they raised rates that they where going to do so which they did June 2004. As far as I can tell or remember there was no retraction to this ‘suggestion’ to lenders and lendees.
Of course now Greenspan is trying to distance himself from this, well he has been doing this since late July of this year I believe or some time not long after that which is when the subprime was just starting to show its head to the public.