Our Spartacus is a friendly fellow too. He has never had a bad experience with man or beast. And we plan to keep it that way if we can.
I do have a funny story about the Mastiff protective instinct.
Spartacus has never shown any aggressiveness to anyone. And we too wondered if push came to shove if he would protect us. We found out on a camping trip.
The Park Ranger came to clean out the fire pit. He had a rake and a shovel in his hands. We had Spartacus on a tether contraction my husband designed with a pulley and a retractable lead, so Sparks can have freedom of movement around the campsite, yet still be on a "leash" at all times as required.
Well, this fellow came walking up with the rake and shovel, and Sparks wouldn't let him in the campsite. Didn't bite him, just stood there and barked and let the guy know he was not going any closer with his "Weapons".
Spartacus wouldn't let ANYONE, even people he knew since he was a puppy in the camp with anything he considered a weapon. (We were on a congregational campout for the weekend so there were 20 or 30 people to keep an eye on.) For instance, No one could bring in sticks for the wood pile, without first putting down the "weapons" and being "checked out" by "security". If my husband or I said it was "ok" then they were allowed to come in camp, but he watched them until the "weapons" were no longer a threat.
One night we were sitting around the fire, one of the guys had a retractable fork, used for cooking hot dogs or marshmallows over an open fire, he opened the fork and there , all of a sudden, right at beside him at eye level, was Spartacus. Spartacus "chuffed" at the fellow, as if to say "Hey, put that weapon away!"
They are good protectors of people. And it is amazing how they think for themselves and deal with people they think are a threat. I find them to be very kind and thoughtful. Our Spartacus is always thinking.