An overdose of patriotism make people blind;
sometimes it can even be fatal - if not to the
person(s) in question, then to other people.

There´s nothing wrong being proud of your country
- if there´s a reason for it. "My country wright
or wrong" is the kind of attitude that has sent
tens of millions of people to their deaths during
the last century, as ordinary, sane people have
followed their leaders to mindless wars, thinking
that they didn´t serve those leaders, but their
country, and that it was their duty to do so,
whatever misgivins they had.