Why argue with your clients? Just start by discussing what their goals are for the site. Talk about their brand and how they will define success for their website. Talk about conversions and features that are necessary to achieve these conversions. Once you have that established, the web 2.0 talk will be a moot point as you'll just be creating solutions that are appropriate to your client's goals. This is the definition of a "good" website. One that's in complete alignment with the client's strategic goals.