Chazaal say in Masechet Yevomot page 48'2'מפני מנה גרים מעונין ויסורין באין עליהם אחרים אומרים מפני ששהו עצמם להכנב תחת כנפי השכינה that geirim get punished for not coming until now. Since there is no reason that they should not see the truth in judaism ,and especially so when being offered to join or when being in contact with them.Therefore we conclude that it is hate and jealousy which prevented them until now.
The Gemarah in Pesochim page 49'2' says אמר רבי עקיבא כשהייתי עם הארץ אמרתי מי יתן לי תלמיד חכם ואנשכנו כחמור וכו' which clearly illustrates the idea that there was potential in him to become that which he became but it was his hatred and jealousy that prevented him from pursuing this venture.
See what hate came out of Arpah and her children upon her declining the opportunity she had together with Ruth.
Now we have proof of their hatred from that, that they refused to be part of us which would have ended the war.
In regular times when the gentile is living their way without anything special occurring we certainly can not draw conclusions from their seemingly ignorance which they have about the true point of the world and in life.