True, its best to avoid highly processed foods. But unless you are buying organic grass-fed beef you are getting a meat product that is highly processed, i.e. cows infused with hormones and antibiotics to combat the effects of being fed a diet of corn that their stomachs cant digest and makes them sick. Some of the veggie-burgers I listed above are made of whole grains, beans and vegetables with no preservatives. There are plenty of less healthy things to eat than that.
Not a store bought veggie burger, but if you want to eat out and try one check out moon tower inns beat burger. It was amazing.