Quran 9:30 “And the Jews say: Ezra is the son of Allah; and the Christians say: The Messiah is the son of Allah; these are the words of their mouths; they imitate the saying of those who disbelieved before; may Allah destroy them; how they are turned away!”
How does the above verse encourage Muslims to fight physically? Allah rebukes those who hold on to pagan beliefs. Allah strongly rebukes those who say the term ‘Son of God’. Those who say such are far away from the path of Monotheism. I would like to mention that, when Allah condemns Jews for saying such, I should highlight to viewers that this belief was held only by a minority in Arabia. Jews in general don’t believe that Ezra is the ‘Son of God’. I don’t want to elaborate any further. We have written a detailed article on Ezra being called the ‘Son of God’ in Arabia, in following article titled: “Ezra (Uzayr) The ‘Son Of God’” As for Christians believing Jesus is the ‘Son of God’, the meaning has changed overtime as Christians started mingling pagan Roman/Greek beliefs into their Christian faith. For someone to be called ‘Son of God’ in the first century, when Jesus (p) was alive, it only meant the man was righteous, a person who is good, a servant of God. I have already written an article on the term ‘Son of God’ used for Jesus in detail, you can read it here.
The Jews say: Ezra is the son of God; and the Christians say: The Messiah, Jesus, is the son of God. That is the utterance of their mouths, for which they have no support, nay, imitating the utterances of those who disbelieved before [them], from among their forefathers, mimicking them. God assail, curse, them! How they are deviated!, turned away from the truth, despite the proofs having been established. 
 Tafsir al-Jalalayn – http://www.altafsir.com/Tafasir.asp?tMadhNo=0&tTafsirNo=74&tSoraNo=9&tAyahNo=30&tDisplay=yes&UserProfile=0&LanguageId=2