We've had these ignorant wars back here in Holland around 2004 when the term AJAX was still a football club in my hometown and a company called BackBase was using a similar UI Dialect like Flex to sell their RIA Product. At that time, there was even a RIA seminar organized by Martijn de Visser at Lost Boys ( from FLV Player fame ) where both BackBase and Macromedia were present. The discussions there were useless and quickly turned into point-to-point comparison which most seasoned developers know is bollocks, there is simply a lot more then choosing a technology based on it's feature-set.
So to whom all it may concert, please keep the discussion honest and useful. Tell people the advantages of Flex but also it's disadvantages. Please do tell them that the Flash Platform excels when it comes to video and animation and even charting. Tell them about the plugin penetration. But also please tell them about it's weaknesses, for instance the text handling. There are similar points made when it comes to AJAX. Not all websites benefit from a total makeover done in Flex. The incremental update with a focus on user interaction ( a gentle notice when a password is not strong enough like in Gmail, an in-page refresh for a newsletter signup ) is what makes it a great use of existing technologies.
If we keep the discussion honest and mature we all ( both us Flash and Flex developers and designers in our Adobe community as well as the bigger web development community ) benefit and can make the right and relevant choice.