I can see why this is an issue for some and how it would fit in with the “Christianity is a copycat religion” thesis of many skeptics. What puzzles me is why another Christian would not see the obvious: we ourselves are former pagans. To say that the Pope’s hat, or an altar, or anything else has “pagan roots” is not fundamentally different than saying a “born-again Christian” or a convert has pagan roots. "Don’t pray with Joe! He has pagan roots!

Preposterous.
We are all former pagans . . .
Second, why is the Pope’s Mitre so funny? I have a simple thesis. . .to make the Pope feel ridiculous every time he has to appear in it. Imagine yourself as a serious intellectual, with doctorates and scholarly letters, articles and books, decades of theological study and reflection and also decades of experience as a priest, bishop, etc. under your hat (pun intended). That’s rarified air, and the temptation to pride could be overwhelming at times. Now, imagine that hat is a Mitre and you have to wear it as you stroll for the cameras and for thousands of ordinary folks, fellow priests, representatives of other faith traditions, heads of state, etc. Kind of a humbling experience, wouldn’t you think?
Isn’t the highest title awarded the Holy Father that of “Slave of Christ?” If the Master says, “you’re wearing the funny hat” . . . well, you’re wearing the funny hat.
My two cents . . .