And I don't object to doing things directly, as you did, even with HTML. I have frequently edited huge piles of HTML with -pi -e 's///' but I would never recommend it (to a junior dev at least) because it's similar to recommending cleaning a loaded gun. I don't mind taking the risk, and even the consequences, myself now and then but I'm not going to suggest it's a good idea to anyone else.
OPs frequently misreport or overly simplify requirements or misunderstand the differences between the cases and unlearning a bad habit is much harder than learning the right way, so I appreciate the dogmatic as long it is also a legitimate best practice. It's easier to say always do ABC than to say you could do XYZ as long as, provided that, but beware, also note bene, caveats apply.
I don't think your advice was incorrect, I was just addressing the why be dogmatic part. :P