Straightening out ALL uneven UVmap vertices in unison w/o overlapping? Instead of tediously straightening all the edges to align perfectly vertical one by one by one, is there some way to straighten out ALL the UVmap vertices ALL at once (like on the left side all nice nice vertical) without having them mashup and overlap into one --as with happens when I select them all and type S + X + 0?
I would just redo the UV unwrapping to get it straight.

Starting with a cylinder. 

Select an edge.


Mark it as seam.



Select all faces.



Unwrap (no special projection, but a straight unwrap).



You should have a straight UV map like this:



Then just scale it to meet your needs.