Among fans of the series, I doubt many would find him to be a likable person or good role model even if they think he's a fun character...

Then they should be able to handle criticism of this character and not downvote me.

The Duke doesn't even do these things in the game!

I realize that's not what you are referring to but

There is no "but". This isn't about what other things Duke Nukem did. This is about the one specific comment I replied to.

the fact remains that it's a game where you can throw a stranger's poop and often find enemies on the toilet... That should be a benchmark for how seriously the content should be taken...

There is throwing poop and there is killing a monster and then defecating onto the lifeless corpse. Those two things are completely different.