The guards don't appear from nowhere, they're big loud men who don't hover silently above the ground.
Big men need to be more careful when marching through crowds who are unaware of their unmarked routes, and be aware that they could seriously hurt someone if they ploughed straight into them, which they did, without reason, and with complete disregard for the wellbeing of the child.
I've seen compilations on YouTube where the Guards simply push adults very roughly, in one case a woman. The TikTok video is now uploaded to YouTube too.
Someone upthread thought there was some comparison between the sentinels at Arlington and the Guards, but there is not. The demeanour of the Guards belongs in a barbaric age.
If you are running a tourist attraction visited by 3 million people every year, and it's almost 2022, maybe your approach should acknowledge that it's crowded, that your ridiculous uniform and all the marching about and staring straight ahead is going to cause people to wonder if you really are a security operative and not a character in a historic re-enactment, and that the Monarch you are guarding is a mere figurehead with no power whatsoever, and none of the trappings of monarchy matter one iota any more.
Maybe you should be honest and clear with potential visitors who do due diligence on your website. Above all, you should decide whether the place you are guarding is a tourist attraction or a terror target, because it is incredibly irresponsible to go on selling tickets to a death trap.