While there is a lot of anti-Polish sentiment and a lot of reasons the Polish should be upset, sometimes they do push it too far and play the victim card. People don't immigrate en-masse to a place that is so horrible to them that they can't stand it. If that were the case, they would never move there.
Polish people have just as much right to be offended as anyone else. You always have to consider the feelings of a particular person or group of people when you talk about certain topics that may be offensive overall. So you can't really say anyone overreacted unless you know where they come from.
I doubt that Polish people often overreact to writings that might be perceived to contain anti-Polish sentiment. If the writings are perceived to contain the anti-Polish sentiment then they probably really do. The Polish people had to deal with Nazi apologists and all sorts of Holocaust denial drivel and victim blaming. I can't really blame some Polish people for being guarded.
No, they do not over react to writings that can be taken as offensive to the Polish people. They expect to see this some, and know how to handle this without over reacting and making a big deal out of it. They may get mad over some stuff, but it is expected.
No, Polish people do not in general overreact to writings that might be perceived to contain anti-Polish sentiment, because there is not a great deal of anti-Polish sentiment, compared to all of the conflicts going on in all of the other countries. In any event, the Polish people have a right to be concerned about anti-Polish sentiment, given the atrocities of World War II.