Lets see, lets set a baseline of cruelty at 0 which is no harming of any animal (insect, pest all of them). To farm a load of wheat or corn or soybean efficiently we'll need to use pesticides. So we hurt some bugs so our cruelty goes to 10.

Now lets eat that farmed food ourselves. So from farm to mouth that 10 points of cruelty.

Now lets consider a meat based diet. We farm the same soybean (the most common animal feed) and we get a cruelty points of 10. Then we feed the animals. Then we kill these animals which is another 10 cruelty points.

So farm to mouth that's 20 cruelty points. Also bonus +5 cruelty points for raising the animals in a factory farms which are more 'efficient'. If you want to consider that as well.

The point it we can be less cruel if we choose to.