this is such bullshit
--means that this thing has the property of bullshit

this is such a bullshit
--means that this thing is the same as bullshit

for example
he is red = his color is red...perhaps he is very hot.

he is a red = he is a communist

the difference between all your examples is whether you are describing the object or acting on the object. a descriptive form could be i dont give shit = i give nothing. whereas an action would be i dont give a shit = i dont care. each has a different meaning.

if you think shit is a difficult word, i think you would love this article

http://www.letssingit.com/?http://www.letssingit.com/dennis-leary-usage-of-the-word-fuck-94xbg4j.html

it is not plural, the liberal weblog community is singular. it is singular for the same reason a flock of birds is singular. there are many birds in the group, but it is still one group and therefor single. since it is singular, has is correct.

had the sentence read the ranks of liberal weblog communities (has or have) increased. have would then be correct because you are referring to more than one community