Those are some of the most pedantic grasping at straws reasons I've ever read. It's like they know there's nothing wrong with http so they've had to invent worst case nightmare scenarios to make their "It's so important" reasons stick. Https is great. I use it. That website is pathetic though.

ISPs injecting ads into HTTP websites isn't a weird edge case. I've seen it happen.

And so what if my webpage about an obscure 1994 Australian rock band get a few ads injected into it? Everything else in my life gets ads injected into it (TV, Music, Movies) Such a silly argument.

The source footer ("View Page Source") summarizes it perfectly:

Sites that need HTTPS: - all of them

If you like it, you better put a lock on it.

And, BTW, the website is as delightfully simple and unobtrusive as the one in the article.