If I saw that "suggested" tip, I would ask to speak to the manager, and explain to them the effect of their "suggested" tip:
1) I will reduce my planned tip by half
2) I will not return to that restaurant until the "suggested tip" policy has been removed
3) I will spread the word about that restaurant (maybe using the aforementioned website - good idea)
Maybe if enough people explained that to restaurant managers they'd get the message.
Yes, I know it's only a suggestion that can be overridden, but to even have an amount / percentage suggested to me is insulting. Leave the decision to me.
It's a bit like getting directions from someone on the street, and then they say, "hey, can I have a couple of bucks for that?". Grrrr....