I'm not against your view, but is the water actually 'wasted'? I think the water you used for rinsing the dishes is recycled in the water cleaning facility. I might be wrong of course, but this water has to go somewhere.
edit: And the cycle is impacted as well, depending on the water flow. Here, water comes out from the aquifier, and is then entered into a river, so it is a shortcut (no spring, no small trickles that join together, and no staying within the aquifier, so the level might be lowered). If this is a problem or not depends on the specific situation.
Which is a process that requires resources that otherwise wouldn't have been needed. A better question would probably be "Is the amount of waste non-negligible?" which I don't have an answer to, but I wouldn't be surprised if it's a lot more than you expect.
The latter if done well should be close to what the dishwasher does, but at this point you're better off just washing manually...