Ironically the rule is that if you attack the person and not the argument you know you're in the wrong. Then again we know such maturity is rare on the interweb
It was a stupid thing of him to come out with to be fair. Indy is a series where drivers may go if they don't get a top drive in F1, but they can be much more competitive there becuase the cars a more evenly matched, not becuase the entire field is worthless.
There has been some poor quality fields in recent years. At last nights first race at Detroit, the commentators actually said the field this year was a much higher calibre than previous years and so contributed to less caution periods. We'll never get a true comparison of how god the top F1 drivers are to the top F1 Indycar drivers until one of them makes the switch, and really you can only compare what they are like on road courses as ovals are somewhat speclialised. Though, when you look at Mansell, he won more races on ovals then he did road courses! If you look at Sato, Chilton & Bourdais, all were mid-grid at best in F1, and for the most part they are mid-grid in Indy cars (Bourdais wiped the floor in ChampCars before he came to F1 but there were some real crap driving around then!), so it does suggest the top Indy drivers are certainly a decent bunch.
Sato in a SA wiping the floor with Alonso in Canada - F1's best All joking apart I still hold the view that you can become an F1 champ and not be the best and you can be the best and not be a champ - or not as many times as you should be. I still think F1 success is more in line with the teams ability and your driver pairing. As an example I still think Lewis deserved the 2007 title over the 2008, Alonso should have won the 2010 and either McLaren driver could have been champ if Lewis and JB weren't paired. Can't speak for Indy as I don't know enough.
There are some very good drivers in the Indy field who would probably do very well in F1, or would have done as some are getting on a bit now. There are also some tracks they race which I would love to see F1 cars on. However, very few have made the transition to F1 and made a success of it. Villeneuve is probably the only one really, and ultimately he was a quick flash in the pan before his ego took over.