The word "wacko" is a derogatory term used to describe someone who behaves in an irrational or strange manner. Using such a term can be considered offensive, so it's important to use respectful language. Instead of calling someone wacko, you can use a variety of synonyms that are more respectful, such as "eccentric", "unconventional", "quirky", "offbeat", "unusual", "unorthodox", "nonconformist", "idiosyncratic", "off-center" or "outlandish". These synonyms convey a similar meaning without being disrespectful or hurtful. It's important to be mindful of our language and the impact it can have on others.