Per the Concise Oxford Dictionary…

“patriotism /'pe?tr??t?z(?)m /
? noun [mass noun] the quality of being patriotic; devotion to and vigorous support for one's country:
a highly decorated officer of unquestionable integrity and patriotism.”

“nationalism /'na?(?)n(?)l?z(?)m /
? noun [mass noun] identification with one's own nation and support for its interests, especially to the exclusion or detriment of the interests of other nations:
their nationalism is tempered by a desire to join the European Union.
?advocacy of or support for the political independence of a particular nation or people:
Scottish nationalism”

The difference between ‘patriotism’ and ‘nationalism’ seems to be very clearly defined there. Nothing to argue about AFAICS.