Most people carry fertilizer and their trucks blow up? Never heard of that. I've heard of fertilizer plants blowing up, and once a truck at the Alfred P. Murrah federal building, but other than that, no. I've heard of fuel tank trucks blowing up too.
Why anyone would want to kill a forest service or BLM employee doing their jobs is beyond comprehension, the people in the field do not write the laws. And you really believe campers are to blame for making pipe bombs and leaving them on public lands?
A person hauling fertilizer in the back of their truck is not automatically suspect of being in a militia or terrorist group.
I think you're stretching or reaching for something here, I'm not sure what though.