If you manage to install software on a user's computer, have it call home, and delete or modify files on the user's computer under remote instruction without the user's permissions you have committed a criminal act in many jurisdictions and immoral act in all of them.
So... license validation is illegal and immoral? Software updates are illegal and immoral? Copyright protection is illegal and immoral?
The OP is talking about selling software, which no doubt would come with reasonable terms and conditions. The buyer would be aware of any 'phone home' checks in place.