I've noted before that religion in Felltower has tended towards the less and less tolerant.
Even the more tolerant Ambassador Durinn has expressed an interest in destroying materials found in the Elder Tongue. Better safe than sorry, presumably.
It's very easy to make a cleric in DF that is intolerant of all other religions (which includes druidism, by the way, and not just the older religions to older gods) or just "evil" religions . . . which usually ends up including anything with even a passing connection to evil (so, magic in general.)
Is it possible to make a cleric of the Good God who is faithful to his religion but isn't a foaming fantatic ready to destroy everything that could be construed as evil? Can you support the Good God and those who worship the Big G, delve for loot and glory, and not feel compelled to trash anything not provably lilly-pure? Let's try.
We'll use a DFRPG Adventurers cleric template, since I have Adventurers handy.
The core three disads don't require a book-burning attitude - Honesty, SoD (Coreligionists), or Vow (No edged weapons). Any of those will do. Let's go with the Vow.
-15 points from those or other traits - we'll need to leave off Fanaticism and Intolerance. The Vows aren't really worth -5 in Felltower, so let's skip those. So it's either Wealth, adding a second main trait plus Ritualism (Mysticism doesn't fit most clerics of the Good God.) Let's say it's Honesty or SoD, either will do.
-25 from those traits or some new ones. I think any of these are fine. Stubborness might be used to justify a tough attitude on non-clearly-Good things, so I'd skip it. The others . . . probably go for it.
All together, you could end up with Sense of Duty (Coreligionists), Vow (n.e.w.), Disciplines of Faith (Ritualism), Charitable, Selfless, Truthfulness.
Seems like a nice guy. Nothing in the religion of the Good God demands destroying anything but capital-E Evil. Nothing says that all sources of knowledge, all foes in the dungeon, all NPCs encountered outside of town, and all non-playable-race-created objects are Evil. Even small-e evil can just be smote if necessary and left to (or shown a way to) find redemption.
That said, those same disads can be paired with a quirk-level hatred of all things that could potentially be Evil and then smash everything you see, but at least you're not forced to be a fanatic. It's a roleplaying choice.