It's not Xenophobia at all.
Gamers can culturally be quite different and saying they have collective traits is not racist. I don't
hate any of the people I play with on L4D2.
We usually play 3 up with 1 random and we all usually have great fun.
Scandinavians are usually great fun, are a good laugh and receptive to banter although we've never had any on voice.
The Germans we've had are similar, they generally have a left field (but good!) sense of humour and we've never had problems. They are very receptive to banter and also receptive to me trying out my GCSE German on them - nearly always a great bunch.
Irish are similar but again never on voice, generally good craic but a little quiet.
The Polish and other Eastern Europeans have been a bit of a mixed bag for us, we've had some of the best games with them - We had a drunk Polish guy once and we literally couldn't play properly because he was making us laugh so much, with his singing and then sudden screaming when the horde turned up suddenly

On the flipside we've had a few rage quitters and plenty of lone wolf types, along with some abusive types.
The French have the lowest fit percentage with us, not sure what it is but we never seem to get on with them very well. Many of them take it very seriously and get upset that we play for more of a laugh.