The problem is that this equates "relationships" and "love" with "sex". The literal text of the law says "don't teach children about sex". The explicit reasoning behind this law is that this means not teaching children about homosexuality.

This positions homosexuality as inherently sexual in a way that heterosexuality is not, which is, of course, not true. Sex is of course an implied part of heterosexual relationships, we're just conditioned as adults not to think about that.