There aren't all that many definitions for 'unite'...Perhaps your church should change the word instead of you having to defend your church for using the wrong definition...
Perhaps no one connected with the translation of the Catechism could anticipate so hair-brained a misreading as we've been shown here.
I promise you if you look upon a text with the attempt to find "gotchas" by bending meaning, ignoring context, and dismissing qualifiers, you can be appalled at just about anything.
It's your choice. Honestly try to understand, or feed your bigotry.