Trouble is, in an international crowd, sometimes people can sound mean or very abrupt - when that's not what they intended. So it's a tricky one. I would avoid if I possibly could in case it's not what it seems.
Also, much care has to be taken about defending people - some people don't want to be defended ...
But, in the end, if totally pushed into it - just give a one-liner and leave it at that.
The other thing is - you've got me going now - that sometimes a deliberate kind of ignoring is the best thing because the mean person can't stand to be ignored and they're often mean simply to get attention.
Of course, all my thoughts can be completely different depending on how much coffee I've soaked up yet. Or not. xx