"Those who curse you I will curse".

ואברכה מברכיך ומקללך אאר When בלק asked בלעם to curse the Bnei Yisrael, he said ארה *לי, "curse me*". Mori V'Rabi Harav Hagaon R.Shlomo.Miller shlita said, In Parshas Lech Lecha, Hashem said," ואברכה מברכיך ומקללך אאר I will bless those who bless you  and those who curse you I will curse". בלק knew of this yet he still insisted on having the Bnei Yisrael cursed. even though as a result of this, בלק himself will be cursed. The שונאי ישראל attempt to harm the Yidden even when they themselves know they will lose out by doing so. At the end of the war,the Nazis ימ"ש, instead of using their  trains for their war effort to save their own military, they used the trains to transport the Hungarian Jews to Auschwitz. Even though בלעם blessed the Bnei Yisroel, he wasn't entitled to be blessed because it wasn't him who blessed the Bnei Yisroel It was Hashem's Brocho coming out from Bilam's mouth.  *see Orach Chaim