Well, he does have some good points...
Poles hate Russians at least as much as Croatians hate Serbs (you're lucky you haven't seen me have discussions with some Serbs online) and for a bunch of very good reasons. One of them is basically constant Russian imperialism towards Poland, including what was basically a campaign of ethnic cleansing that started in Imperial times and then intensified under the Soviet regime.
And looking at history, having ethnic minorities within the country is dangerous because they are almost always certain to work against the country in question (much like Croatian Serbs worked against Croatia from the time they were created from Vlachs in 19th century all the way until today). Basically, if you look at prominent leftists and leaders of leftist (especially Communist) movements in any given country, they are all too often members of some minorities - neither Lenin nor Stalin were ethnic Russians for example (Lenin was a mixture of six different ethnicities, Stalin was a Georgian). That is why the Left always supports immigration: they know immigrants will vote for the destruction of their new home, and we had seen this with recent elections, where leftist candidates had a far greater proportion of minority and immigrant votes.
The idea they had after World War 1 (and then again after World War 2) of creating ethnically homogeneous countries was a very good one, and had it been honored, it might have prevented a lot of pain afterwards - beginning with World War Two, to war in Yugoslavia and even the current war in Ukraine.
And this is actually the cause of this entire shitshow in Ukraine. Soviet government had deliberately settled Russians into Ukraine in order to keep the republic under control, and hopefully forever a part of the Soviet Union. Country that is busy falling apart cannot rebel, after all. And even now that Ukraine has become independent, Russian colonists are still perfectly doing their job, as can be seen from the entire current situation. Much like Serbs in Croatia had acted as a fifth column - for Habsburg government, for Royal Yugoslav government, for Tito's Communist government, for Slobodan Milošević and now for Bruxelles and Belgrade both - so the Russians in Ukraine had been, are being and will be used as a fifth column for Moscow.
Even if they themselves, perhaps, do not want it.