The Torah commands that we teach Torah to our children, a command which includes teaching Torah to the gentile proselyte because the proselyte is like a new-born child:
Yevamot 48a "R. Jose said: One who has become a proselyte is like a child newly born. Why then are proselytes oppressed? — Because they are not so well acquainted with the details of the commandments as the Israelites.
More than this, the proselyte is an orphan:
"The reason for the prohibition 'You shall not wrong a stranger' (Exodus 22:20)...is that he has no family roots" (Ibn Ezra's short commentary to Exodus 22:20)
Therefore, one distorts Torah to the proselyte is susceptible to the following curse:
“Cursed be anyone who perverts the justice due to the sojourner, the fatherless, and the widow.’ And all the people shall say, ‘Amen.’"(Deut 27:19).
Therefore, the teachers who distort Torah for proselytes must be rebuked because we are commanded:
"You shall not hate your brother in your heart: you shall surely rebuke your neighbor, and not bear sin because of him." (Lev 19:17)