Ok despite all that, the bottom line is that to generalize about this topic is to say the least, dangerous.
It depends on the back injury (or surgery) and whether or not you can actually bring it back to full function. No matter how bad you want it, depending on the injury, you just might not be able to get it, and wind up making it worse. The ONLY way to ascertain this is through consult with qualified professionals.
I've brought my back a long way from where it was over the years. But I will never be able to max out my squat. I can put myself in bed for a week by loading up what should be a mere "respectable lift". I still squat but modestly and very carefully.
To advise someone with a back injury to work on their lifts, without knowing what exactly their injury entails, is IMO just bad advice and foolish. What runs through the spine again? There's a reason old people toast to good health and no lower back pain.
Pulling some muscles in your back vs. damaging the actual vertabrae, tissue, or cord are two VERY drastically different things that can impose significantly different lifetime limits to what you can and can't do. Sometimes surgery can do wonders, sometimes it can't.