It depends on how negative they are towards my social contacts and that of myself. If they are on the extreme side with their negativity, then I no-longer connect or network with them.
Now, if its just a few isolated incidents, I address it with them and then keep on moving, because wasting time like that will cost me some digital earnings in the end and I cannot afford to lose any of my online potential of reputation due to a rotten connection, or rotten apple in the bunch.
I hope this answer suffices, and its my best advice to pretty much evaluate the circumstances surrounding such negativity detected. Avoiding it sometimes is impossible, and especially when an entire community may be infected by such people.
Good luck in any event on your online travels, and thanks for asking such a good question!