Talk about 'ethnic differences' and attitudes thereto is usually conducted, in educated circles at least, in a very constrained and politically correct manner. No wonder. A word out of place - or the wrong word - can destroy a career.
This situation is unfortunate because there will always be those who - feeling that they have nothing to lose - are only too ready to fill the vacuum with ugly words and ugly deeds.
On the basis of evident racism in elements of the far right, the left tends (incorrectly) to see anyone right of centre as suspect in this regard. I think I am correct in saying that the left particularly prides itself on not being racist (whatever that means exactly [see below]) and sees this as a key point of differentiation and self-definition. So if racist ideas can be imputed to conservatives, this serves to sharpen the left's self-identity.
Racism becomes politicized - which means it is ever more difficult to deal with the deep and complex problems associated with ethnic tensions, and ever more difficult to discuss these issues sensibly.
In fact the words 'racism' and 'racist' have become rhetorical hand grenades without any clear meaning. Sure, racially-motivated violence, racially derogatory language and certain forms of discrimination can be seen clearly to be racist. But even those who merely interpret data garnered from cognitive and other testing of various populations as indicating significant statistical differences between those populations with respect to specific abilities may be accused of racism.
These implicit constraints on free inquiry and free speech only serve to create resentment and cynicism.