Everyone's comments were excellent, pro and con. If I find any other 'readable' academic pieces here I will post them -- some are just beyond comprehension to anyone without a PhD in horticulture or biology. Or Latin.
I think the consensus is fairly good here that feeding squirrels the nice, ripe, green center part of a good avocado will NOT hurt them and will make them very, very happy. As for allowing squirrels free reign to eat whatever part they want -- we'll leave that up to the individual squirrel person, with a cautionary note.
It's like grapes. We know squirrels choke on grapes. Some of us still feed them grapes....some cut, peel, and de-vein the grapes before feeding....and some (like me) pretty much just avoid feeding grapes at all unless we're sitting there watching the squirrel eat it. Like my financial advisor says to me all the time: it's a matter of how much risk you are willing to live with.