Using a Heat Gun

• heat with heat gun (around 500F)
• remove with pliers and screwdriver.

Works Well!

Using a Hole Saw 

• Find a hole saw that is about the same size as the pipe.
• Heat the hole saw with a torch for about 1 minute
• Place hole saw in fitting for 1 minute
• Remove fitting with a pair of needle nose pliers.

I couldn't get this to work.

References