Hold ALT and do what now??? By the way, the Python approach does not work for me and I can't figure put why, I've gone through this 6 times in a row, checking every single character and for typos, but it always results in error. Am I missing something? 
pointoflife14 "False" has to be capitalized ☺️
But with modern Blender if you hold ALT when you click any checkbox (like Auto Texture Space) it will also check that box for all selected objects. Likewise holding ALT and clicking (or dragging) to select all texture size values will apply the entered value to all selected objects as well.
Which is much easier than the python method. BUT now you know how to write a little macro with python!
Capital "F"...Boom! That's what I was missing. Thanks Kent. By the way, on my MacBook Pro, holding Alt and clicking anything only makes the page scroll. What do I need to change (or enable-disable) to get the "Alt-Click" feature to work as noted?