They existed, it's just that it takes a lot of courage to speak out against deplatforming ISIS, so most people just stay silent in public. I was fairly outspoken about defending their right to expression, but that was only to "safe" groups of friends rather than the general public. (Of course, now that ISIS is basically dead I can be a bit more free with my words and admit to disliking them being censored)
Regarding your kids agitating example, as a society we already do plenty of brainwashing of kids, it's why our ideas of right and wrong are so different from 200 years back.
Also, we had near absolute free speech on most of the internet for most of the 2000s, so your fearmongering there rings hollow.