Is it social suicide to delete all my social networking accounts?

[Colin]

You and they have different personalities online than in ordinary reality. So go ahead and delete, it just means you like the ordinary real people more than their online selves.
In my case I have a lot of "lurkers" ie people who read but never write, which at least avoids getting into an argument. Put a post, more or less what you have said here. Wait a day, then delete.