I think that Reddit tends to have a bit higher level of users than the typical site. The mods of each group spend a lot of time curating the content - unpaid. Most users and Reddit itself know that pissing off the majority of this group that actually produces their product for free could have negative consequences, and they'd end up like Digg without much warning. It seems that Reddit's way forward is not with ads or affiliate links, but paid content in the form of up voted articles and comments. It's becoming quite noticeable.

Are they toxic if they are the primary reason the website exists?

Reddit was successful in the early days due to the quality of the comments of its userbase. It got diluted after the user base expanded.

However, qualifying it as toxic only means that if you were head of Reddit, you would probably run it into the ground like Digg.

I'd say so, but when they make up a not insignificant amount of your userbase, can you afford to just ignore them?

If 60% of your users don't want your company to make any money, maybe you need 60% fewer users.