After finding someone that you share values and ideas with online says one little thing out of place, mark it as a red flag if you need to, but don't throw out the baby with the bathwater. I'm talking about the initial interest and topical vetting that typically occurs from they way they write using vocabulary, sentence structure, comprehensive thoughts, or how they treat you in words.
If using online as the metric, once you determine someone is interesting, make an effort to talk, video chat, or meet in order to get a better sense of who they are instead of inferring from your interpretation of what you read. How much of yourself are you inserting into what the other person typed? Without body language, tone, and linguistic cues, text alone shares about half of the story.
So, where is the other half coming from? Your own experiences, whatever pain, fear, hopes, or hesitations you have are going to make up the other half. Before jumping to conclusions or contesting this statement, I stated above "after finding someone", so you've already got over the initial profile vetting that needs to occur.
The risk that YOU WILL sabotage a good candidate or possible relationship increases the longer that it stays in written word only. Once you get past that barrier, make an effort to speak to them, in a call or video chat. It will open up whole new possibilities and will remove some of the personal injections that we've already made into the conversation.
This behavior only results in closing communication and you'll never have a healthy and open dialog in a relationship by doing this. It also puts up walls in others that are wounded by this experience. One misunderstanding or misstatement shouldn't be cause for cutting someone off, it should be a chance to see how they react or clarify it, and how they react when you open communication.