I respectfully disagree. While I think you are spot on about the ridiculousness of the procedure, and how much more likely it is to cause harm with a LSB than to actually prevent harm as was intended, I think you can still get sued by walking a patient to a board.
You are correct, the standard of care in medicine is to remove LSB as soon as possible and generally the patient is left in a collar (at least around these parts). The problem is that doing standing take downs and whatever to back board people is the standard of "care" for EMS, it's how we were trained, and that is the expectation. All a lawyer needs to do is find an educator or clinical director or whatever backwards thinking dumdum we have rampart in our profession to say "It is expected that paramedics back-board patients in this manner", and then find a neurologist to say "I suppose it's possible that the patient walking/climbing to the back-board exasperated his spinal injury". No matter how false or exaggerated any of this stuff is, that alone would likely be enough to sue you. Not to mention if you don't have "selective" spinal immobilization protocols you could really be screwed. Plus there are cases of paramedics getting sued for not back-boarding someone, or not administering oxygen fast enough. All it takes is a smart lawyer and a dumb jury.
With that being said, I do exactly the same things you do NYMedic. I almost regularly walk people to the backboard (not far though), I have had a patient on rare occasions and under certain circumstances climb into the ambulance to be boarded. I personally think both are totally safe. While it would be better if I didn't have to board these people at all the reality is that anyone complaining of neck pain/back pain/drunk and fell/old and fell the expectation for us is to board, so I board in the most back-saving way possible to CMA (cover my a$$).
Basically, I think you're right in what you do, heck I'm the same way, but I'm fully aware that if one of my supervisors saw me or a lawyer wanted to get me I'd be hung out to dry. I cannot defend walking a patient to the board because if they have to be boarded I have to follow my protocols on how it's done... and they definitely don't say "walk patient and have them sit on the board". It sucks but it's the reality of being a certified technician...
As a small side note, as a paramedic you are extremely unlikely to be sued. I make $40,000/yr, no one is going to get rich slamming me with a law suit. I actually can't think of a single time I have read of a paramedic getting sued. Your employer however is very likely to get sued if someone is looking to go after you.