But why can't you raise the min wage to $40/hr? 
Thats the point being made.
You can't assert "raising the min wage doesn't hurt businesses", then say "raising it that high will hurt businesses". 
What proponents need to do is clearly state what kind of raise they are talking about. Otherwise you open the door to this extremely tired argument...
Now I know asking the left to be clear is a tall order, and its unlikely to happen, but it would be nice. 
Raising the minimum wage
too high would obviously hurt businesses, but that doesn't mean that there shouldn't be one.
There's a trade-off between job losses and benefit to low-wage workers. If the min-wage is too low (or nonexistent), then low-income workers get exploited and we end up with an unnecessarily large amount of people getting government assistance. If it's too high, jobs start getting cut and many of these workers end up on gov. assistance anyway due to lack of jobs.
So the thing to do is to try to find the sweet spot where where the benefit to low-income workers (in terms of wages) outweighs job losses.
I dunno exactly where the sweet spot is, but at the moment I'm of the mind that $15/hr might be a bit too high (not that I think it'll bring the city down or anything, just might lead to too many jobs cut). Personally I'd say set it somewhere in the $10-$12 range and somehow index it to inflation, and go from there.
