The word “relative” means the same thing as “relevant”. This in itself is not a problem, but the term “relativism” is the name of a moral philosophy. It means that what is good or bad is “relative” to the opinions of the people involved in a situation.
Someone may believe that lying is bad, but then say that it is good to lie if it saves the life of someone. It is hard to come up with an example of how telling a lie would be good. Even if someone can come up with a situation like that, I know that I could not lie to protect myself or another person. If I am aware that telling the truth in response to a question could have a bad result, I can stay silent.
But relativism also implies that there is no standard of truth or morality. If morality is just a matter of opinion, then I only need to say that my opinion is that there is an absolute morality that has always existed. Someone could tell me that I am wrong, but then it is their word against mine. If two people say completely opposite things. One of them is true and the other false. Pretending that something is true and false at the same time is a contradiction. A person can only do this if they are confused, dishonest, or have not yet noticed the conflict.
Just because something is true does not mean it is good. It may be true that an act is bad. There may be an action that is good but that no one has had the courage to do.