I think the point being made here is that many people clearly enjoy what Starbucks offers. So, saying they suck is preaching to the choir. The only people listening to that are the people you aren't trying to convince. If you want an impact, suggest an alternative that will make those people happy. To do that, start with an understanding of the value Starbucks brings them. Failing that, you are just signaling that your thinking isn't for them. They'll just ignore you and continue to happily give Starbucks their money.