Antonyms for the phrase "took one's side" could include "opposed," "disagreed," "challenged," "rejected," or "withheld support." These antonyms suggest a lack of agreement or alliance with someone, perhaps due to opposing beliefs, values, or opinions.
When someone takes a different side than us, it can create conflict or tension in our relationships. However, it's important to remember that everyone has their own perspective and experiences that shape their beliefs. By respecting these differences and engaging in open, respectful dialogue, we can learn from each other and find common ground.