Why is my avocado tough and rubbery?
It's simply not ripe yet.

Don't buy avocados or any other fruit and vegetable in pre-packed bags, because you cannot tell what state they are in.

Buy from a local grocer whom you can trust, and therefore can get honest answers on the state of the produce.

Avocados are usually sold unripe for shipping reasons. Buy ahead of need, and let them ripen at room temperature (2 to 7 days). They will keep in the fridge if you need them later than that.

To recover a peeled unripe avocado, you can cube it, and then cook it in the microwave in short bursts to soften it. It's only good for salsa or sauce at that point though. One advantage of slightly cooking avocado is that the green colour becomes more intense; I suspect this explains the guacamole colour from many fast food vendors. :-)