If the base then hire a pro... or is each stanchion post bent along its length?

If the latter, then you could use a press without putting too much side load on the bases. I'd make a jig out of wood by using a cove bit to shape the edges of two wood boards (2x4 or 2x6) and use the strongest clamps you have to squeeze them together and straighten the stanchions. You'll need to sandwich the shaped boards between two other boards (with more clamps) to keep them aligned because the shaped boards will want to flip sideways under clamping load.

If the stanchions spring back from the straight shape then you might need to cut more boards with a curved edge to bend them a little past straight.