I understood what you've said, and I've criticized it. "I don't like you" is also a common phrase, easily understood by most, and appropriate in some circumstan

I understood what you've said, and I've criticized it. "I don't like you" is also a common phrase, easily understood by most, and appropriate in some circumstances; but similarly, these circumstances are unlikely to come up when speaking to strangers in an online forum, so it's generally just a rude and unnecessary thing to say, and takes the discussion in a toxic direction. Criticize people's ideas and leave them out of it. It's a basic courtesy that keeps the community healthy.