Love is shown by really listening. By understanding how your child feels even if you must not agree. It's OK to say "I don't agree". Say it, have a respectful conversation about it and set any boundaries that you consider need to be set. Just make sure you allow your child to express his feelings and thoughts, and don't judge him. If you do, your child will close up, your communication channel will break down, your relationship with him will suffer and so will he.
It's OK to say "I don't agree" and set a boundary. It's not OK not to listen or to judge.
To great family relationships!