Cynicism - “a sceptical, scornful or pessimistic attitude; an emotion of jaded negativity, or a general distrust of the integrity or professed motives of other people” ~ en.wiktionary.org
Cynics suck the energy from others because they feel that they haven't the ability to generate their own and cynics generalise so there is no real opportunity to respond to them.
Having said that, they preserve the balance in life.
A (generalised) viewpoint
‘CYNICISM - The cure for bliss’ T-shirt available from zazzle.co.uk