There's nothing really to "prove". It's just a basic understanding of how journalism works. Have you ever been interviewed before? I have on multiple occasions (both TV and newsprint). It's amazing to me how just much footage or dialog they collect and how the majority of it isn't used. You can sit down for a 15 to 20 minute interview only to have all of 5 seconds of video or a single quote show up in the final product. In some cases it can even involve multiple takes of the same question. (Imagine answering the same question over again just to get a better 'version' of it).
You can find out this for yourself if you follow any Youtubers who do interview style videos or other videos involving the public. I follow some Youtubers that have talked about the process. Street magic videos are a good example of this. Street magicians will film hours of tricks with various pedestrians and then cherry-pick the very best results. Any times the trick failed or they didn't get a good reaction from the participants, they don't use that footage. They just take the best responses. The result is that a dozen or more hours of raw footage can get distilled down a single 20 minute or so video.
It's no different with what Ray Comfort is doing. He probably collected dozens of hours of video footage over multiple days solely to put together a single 1 hour video. Naturally all the times people actually rebut his questions or laugh at him or whatever, he's not going to show. He's given you a carefully constructed and highly biased end result. After all, you're not seeing everything that went into making this, only the finished product.
Maybe you expected to post that video here and think we'd have the same sorts of reactions as his interview subjects. But what you're seeing here isn't edited or filtered. Those of us non-believers who are familiar with Ray Comfort tend to think he is a joke. Hence, we're not falling over in amazement, we're just laughing at him.
If you really think a Ray Comfort-style video is a true representation of a discussion (and attempted conversion) a non-believer then you really have a lot to learn.