There are many online situations that can result in our words being misconstrued, as you've noticed - I figure it's because so much is actually missing - such as tone of voice, facial expression, etc. - so that a person's interpretation of written words ends up reflecting the reader's attitude (which might be different from the attitude of the writer). Therefore, it can result in written words not resulting in very effective communication. Nevertheless, it can be valuable opportunities to try to express oneself (online). So, try not to take things too personally when using online.