I agree with those saying that it's a sorry state of affairs when one of the richest countries in the world has to have community shops/food banks.
I like the idea of supermarkets putting their surplus/waste to good use (although really I think measures should be in place to prevent waste before it gets produced, IYSWIM: anyone read that article in the Guardian where there were cheap Jaffa Cakes in the community shop because they were unfit for sale in a 'proper' shop due to being either a bit below or a bit above their advertised weight? 
)
HOWEVER OP, I take exception to the sentiment that it will encourage people to 'spend their benefits on non essentials and think its ok because theres always things like food banks etc to fall back on.'
First, how humiliating and soul-crushing do you think it would be to have to go to a food bank? Really, just try to put yourself in that position, just for a second. Do you honestly think people feel so sanguine about it that they'd happily use it as a fall-back, rather than as a last resort?
Second, how DARE people spend their benefits on 'non essentials', eh? And what are 'non essentials' in your book, anyway? No, hang on, let me guess: maybe people on benefits shouldn't drink, or ever have, say, chocolate, or a cigarette.
Even if people do abuse community shops, it will be a tiny minority (just as it's a tiny minority who abuse benefits) and, in my book, you don't create or run or judge a society by the standards of its worst but continually strive to raise it and keep it at its best.
In short, IMO your OP is pretty offensive. And if you think I'm one of those 'angry people': well hell yes I am. I am angry at the government who have made food banks and community shops necessary and those who voted them in. And I'm angry at people who continue in the face of all reasonable evidence to put down and demonise people who have to live on benefits.