The problem is that word "Ruski/Ruska/Ruscy" is associated with the attitude of Poles towards Russians and Russia and I think it quite often stems from it. Not always, not in your case, but quite often it does.
By "attitude" I mean this:Which - according to the general Polish stereotype - so we find the eastern border ? First of all - the Russians . The Russians , which include both the Russians and the Ukrainians and Belarusians , because the average Pole barely three nations from each other distinguish . Often the " Russian " we throw the bag yet - Polish generous hand - Lithuanians, Latvians and Estonians , but recently it happens now - thankfully - less frequently. The Baltic States are together with us and the EU and Schengen , and the Estonian - which is the statistical information they already suppressed admiration assimilated - anything you can get on the Internet and pay for parking SMS - em.
And the "attitude" as shown in this quote from the article:
Ulrich opowiada jak pewnego dnia jechał busem do Mniowa na dyżury terapeutyczne. - Jakoś tak zeszła rozmowa na temat Luby. I ci ludzie, do obcego w końcu mężczyzny, jakim dla nich byłem, w ogóle się nie krępowali. Ruska to, ruska tamto, epitety, pamiętam ten rechot Leppera w całym busie. Wtedy zrozumiałem, jak Luba może się czuć na tej wsi - opowiada.
Even in Polish dictionaries this word is described as "disrespectful" ("lekceważący"):
I've noticed that Russians tolerate this word only when it's coming from some hardcore rusophiles.