Ok, I am going to come clean.
I am a lover of languages. As a matter of fact, English is my second language. My love-language, a language of choice. I have working knowledge of at least 4 more languages and would take up another language at the drop of a hat. As a general rule, the benefits of learning a foreign language are faily obvious.
But, and here comes the but. Language brings with it a whole culture and political environment, and the people of a country it is spoken in. If you want to protect your child from an influence of a culture you are trying to get away from, you protect it from learning the language of that country.
An example of such a choice is Ben Yehuda, who protected his children from any language but Hebrew.
In his book ‘A Tale of Love and Darkness’ Amoz Oz is talking about his parents, who while conversant with seven languages each, ensconce their children in Hebrew only, as if to protect them from the horrors of Europe.
I come from Russia and, against the constant and vocal complaints of fellow-immigrants, have not cultivated Russian in my children. If I have anything to say about it, they will never cross THAT border. Not knowing much of the language will protect them against the temptation to do so.