There is nothing insulting in the bit you quoted. It describes someone from a rural background who turned a teenage racing hobby into not one but two careers. Maybe you're so sensitive to country folk getting shit that you think just mentioning his rural background must be done with a snicker and a sneer, but I don't. It's the plain facts.
And "grease monkey" is not an insult. It's more of a compliment, if anything.
If it is such a compliment, then why not go to an auto shop and say "Hey you grease monkeys, how are you?" and then see if you get punched. I am not brave enough to do that, and I have been working in automotive for 25 years.
It would not be the same as talking to computer programmers and calling them 'hackers'
And "grease monkey" is not an insult. It's more of a compliment, if anything.