yes since they have already overran & conqured Myrtana, they have earned the right to be scornful of humans. this makes the liberation mission more realistic and purposeful.. something like out of 'the planet of the apes' movie.. i feel like the crash-landed astronaut from that movie..Absoluttely, they got that tone just right in my opinion - I always get this feeling the orcs look down on humans in general, just from the way they talk to/about humans.
Everytime an Orc says that it reminds me of something that the Dunmer used to say to me in Morrowind. I can't remember what the word was but it was said in a very similar tone.