Antijudaism was the early form of antisemitism, before Christian Europeans in the early 19th century came up with racial, "scientific" antisemitism. There is no evidence that he "loved his Jewish brethren", and plenty that he didn't care very much about them.
I disagree. I was raised Catholic, but I don’t hate Catholic people. Most of my extended family are Catholics whom I love. I only grieve that they are caught in religious bondage like Paul did for the Jews bound under the laws they could never fully, nor perfectly keep. I am not denying that anti-Semitism has been a real and major issue throughout history perpetuated by various groups, including organized Christianity, but to be anti-Semitic is a sin. The Catholic Church and most Popes were were notoriously anti-Semitic. Even Martin Luther expressed some pretty vile anti-Semitism. No true Christian who is submitted to Christ can be against the Jews. From my perspective anti-Semitism is inspired by directly by satan.
Paul loved and grieved for his Jewish brethren, notice verse 2 and 3...
I tell the truth in Christ, I am not lying, my conscience also bearing me witness in the Holy Spirit, 2 that I have great sorrow and continual grief in my heart. 3 For I could wish that I myself were accursed from Christ for my brethren, my countrymen according to the flesh, 4 who are Israelites, to whom
pertain the adoption, the glory, the covenants, the giving of the law, the service
of God, and the promises; 5 of whom
are the fathers and from whom, according to the flesh, Christ
came, who is over all,
the eternally blessed God. Amen. Romans 9:1-5