The goal is fun. Do what is fun for you.
I liked Duke Nuke'm 3D back in the 1990's. I finished it several times, with invincible cheat on. Why? I found it most fun running around, blasting bad guys into chunky salsa, and laughing like an idiot.
With my current MMO, City of Heroes, the difficulty settings are very flexible. Some days, I want to steamroll helpless mooks, and quash laughable "Bosses" with aplomb and contempt. Other days, I want to sweat and bite my knuckles with every fight, and EARN the final victory.
Your buddy may have one of those "Stop Having Fun, Guys!" jerks. If you aren't doing it his way, you are wrong/weak/stupid/"casual"/etc. It's your game, it's your time, so have your fun, your way.