Why the hate for mcintosh amps?

I guess that the different speaker binding posts connect to different windings within the Autoformers.

Since the output transformers allow for 2 4 or 8 ohm

why not a single/universal connect to speakers that can handle all 3?.?.?

Has to do with "output impedance" of said transformer tap. (damping factor) into the speakers impedance to control the speaker cone movement, and getting the "most wattage" without losing control for that speaker driver.
The lower the transformer tap the lower the "output impedance" the higher the "damping factor", penalty is the lower the tap the lower the wattage also.

Cheers George

Spkr says rated for 8 but told to use 4 , b&w 802 d3.  Does it matter?

lower the tap? Is 2 lower than 8?

Who told you to use the 4 ohm tap? Users do experiment. There is no 2 ohm tap, so what did you mean "is 2 lower than 8?"

There is a 2 ohm output connection onback of amp.

is it ok or advantageous to use 4 ohm connection?