Why are the goblins so rude in fanfiction?

In a vast majority of fanfiction, the goblins are portrayed as savage rude beasts which are activerly wanting to kill people. This bothers me as in the books (PS at least), they are shown as quite polite.

Exerpt from PS, Chapter 5 page 56

‘Gringotts,’ said Hagrid. They had reached a snowy-white building which towered over the other little shops. Standing beside its burnished bronze doors, wearing a uniform of scarlet and gold, was – ‘Yeah, that’s a goblin,’ said Hagrid quietly as they walked up the white stone steps towards him. The goblin was about a head shorter than Harry. He had a swarthy, clever face, a pointed beard and, Harry noticed, very long fingers and feet. He bowed as they walked inside. Now they were facing a second pair of doors, silver this time, with words engraved upon them:

The guard bowed to them, not sneered or snarled as they often do.

The next page, a new pair of guard again bows to them, before Harry and hagrid enter the main hall. this next bit is from that same page, when they first go up to a goblin:

Hagrid and Harry made for the counter. ‘Morning,’ said Hagrid to a free goblin. ‘We’ve come ter take some money outta Mr Harry Potter’s safe.’ ‘You have his key, sir?’ ‘Got it here somewhere,’ said Hagrid and he started emptying his pockets on to the counter, scattering a handful of mouldy dog- biscuits over the goblin’s book of numbers. The goblin wrinkled his nose. Harry watched the goblin on their right weighing a pile of rubies as big as glowing coals. ‘Got it,’ said Hagrid at last, holding up a tiny golden key. The goblin looked at it closely. ‘That seems to be in order.’

‘An’ I’ve also got a letter here from Professor Dumbledore,’ said Hagrid importantly, throwing out his chest. ‘It’s about the You- Know-What in vault seven hundred and thirteen.’ The goblin read the letter carefully. ‘Very well,’ he said, handing it back to Hagrid, ‘I will have someone take you down to both vaults. Griphook!’ Griphook was yet another goblin. Once Hagrid had crammed all the dog-biscuits back inside his pockets, he and Harry followed Griphook towards one of the doors leading off the hall.

The teller is polite saying "sir", and is accomodating to Hagrid's letter from dumbledore. Yes, he wrinkled his nose, but who wouldn't if someone emptied they mouldy dog bisquits over your workplace?

I won't bother pasting every goblin interaction in the books, but the last one might have been interpeted wrong:

Vault seven hundred and thirteen had no keyhole. ‘Stand back,’ said Griphook importantly. He stroked the door gently with one of his long fingers and it simply melted away. ‘If anyone but a Gringotts goblin tried that, they’d be sucked through the door and trapped in there,’ said Griphook. ‘How often do you check to see if anyone’s inside?’ Harry asked. ‘About once every ten years,’ said Griphook, with a rather nasty grin.

I don't think this is the warrior race of goblins showing their true colours, i think this is a bored banker having a bit of fun teaching/scaring some knowledge into a kid.

​

Nowhere in the first book did the goblins act anything other than professional. Why then are they such beasts in fanfics?