This is great advice for me to hear, as I'm in a similar position right now. I've been considering obliquely slamming our competitor in a blog post, but I've held off because I don't want us to come off like dicks. Wouldn't I be better off focusing the messaging on how we're doing it right, rather than how they're doing it wrong?
You can define yourself and, through the remaining empty space, end up defining them. If you define yourself as "The simple, no-frills, easy way to Foo," for example, then you're defining your opponents as one or more of: complex, extra frilly, less easy.
Publicly slagging off competitors by name seems to backfire more often than not, unless you're Steve Jobs.
However you can talk about all the ways that X is done wrong without actually mentioning by name the competitors who are doing X wrong. Clearly explain the problems you see in 'the industry' and your solutions to them, but not the other people/companies involved.
