Dan whilst I never worked with KLM I did fly with quite a few Dutch; my only trip request in my whole career was with a Dutch skipper and I had a couple of other good colleagues; there were more than enough mean, racist and unpleasant ones.
The last one I came across was an ex DC10 skipper in my gliding club who tried to sell me his motor glider without telling me that there was a serious engine ignition fault that could have killed me. A real user whom I did lots of favours for when he decided to move to france. I had another dutch colleague who was extremely mean - he was executed and his body dumped in a canal in Amsterdam.
I worked for the best paid European carrier..my wife left the country after a little more than two years because of the racism.
After 13 years in the company I got my command and caught a blond, blue eyed station manager thieving from the aircraft which she had delayed because of her laziness; I asked for her name after I bollocked her but didn’t put a report in- she did which was a pack of lives which my chief pilot believed. For various reasons this hampered how I could perform my job and in the end in spite of taking 20 years overall to get a command I told the chief pilot that unless he believed me I would go back into the right hand seat.
That sorted it out BUT I was constantly being downgraded on staff travel flights by her mates.
Tip of the iceberg including wife not being fed on a 14 hour flight with the CC throwing away a fillet in front of her..Layovers with all the crew bar me on Christian name terms with captain. Loosing the equivalent on fifty grand on Passover pay and a quarter of a million into my pension fund when I lost my medical.
BUT there were a lot of good people and they’ve been paying me a pension ever since.
Speaking the language helped and imho is a must although many of my foreign entry didn’t both. What was difficult was saying no to the young hostesses who wanted to try a bit of foreign because their countrymen are so boring; got very expensive so some.