This is a workstation configuration setting that you can change in this way:

-cd into /usr/dt/config/C
-in the C directory you will see a file named sys.dtwmrc
-copy this file to your home directory
cp sys.dtwmrc $HOME/.dt/dtwmrc
-open up the copy you saved into your home directory in a text editor
-If you scroll down you will see the heading "Buttons DTButtonBindings"
-There are two lines here that you want to remove
Alt Btn1Down icon|window f.move
Alt Btn3Down window f.minimize
-Save your changes
-Log out/log back in

You will now be able to use the ALT + right mouse button to spin your view in
Inspection.