wvmarle:
This shouldn't be an issue with an AC load, thanks to the current dropping to zero 100 times a second (or 120 times if you're on 60 Hz).
No, it very much is an issue with an inductive mains load - you don't understand what happens when
breaking a highly inductive circuit - arcing damage is done on a much shorter timescale than a mains half-cycle,
and the high voltages generated can compromise the motor winding insulation or the motor wiring if not controlled too.
A 1.75hp motor may pull many tens of amps worst-case (at start up or stalled), and if that current is interrupted kW or tens of kW are directly available to pump into the arc and damage/weld the contacts as the magnetic
energy in the motor returns to the circuit rapidly.
If you are lucky the motor has some snubbing built in, but you'd have to check for that.