All three of those can be easily written off by anyone who likes the project. Claim that 4chan is toxic; people who like 4chan will think you're an idiot, but it won't really ruin their mood. Point out specific examples of their favorite board criticizing something they love, however, and they probably will feel upset for one reason or another.
But in a public forum such as this, calling a community toxic can, and will, keep people from looking in to to the associated project any further. If you have specifics, you should say them - public spaces are the right place to out toxic communities. But, people on the internet throwing around words like "toxic" without substantiation can be really damaging to communities by preventing growth.
Please substantiate - I'm not involved in the Nix community much but whenever I've been in the #nixos IRC channel, they've been super helpful.
