May be I'm too stupid.. but I hope I'm not!
A rectangle is orthogonal.. meaning the adjacent lines are perpendicular. A
a non-orthogonal rectangle would have angles <> 90 degree.. So it would not be a rectangle any more.
I assume you would like to draw a
parallelogram, or may be an
isosceles trapezoid. But first can not be defined by two points. You need 3 points. So pressing ALT is not an option.
If you like to draw a parallelogram, draw a rectangle and stretch one of the lines (select complete line to get BOTH ends).