The professional - i.e. presumably paid, but either-way apparently 'full-time' - blog troll is an interesting phenomenon. It could be said that you have only really 'arrived' as a blogger when such persons begin to pay you attention...
My assumption is that such individuals are recruited by the global Establishment as a cheap way of subverting nascent sources of Reality or Good - a single troll can cover a lot of virtual-ground (using various false names, and multiple accounts).
In other words, Christian bloggers should be encouraged, rather than annoyed, by the arrival of professional blog trolls! - since it is strong evidence that you are having an effect (or at least, the powers of strategic evil fear that you may become a threat to their plans).
What are they trying to do? Two things mainly - degrade the quality of the blog so as to put-off readers, and demoralise the blogger by wasting his time answering a never-ending stream of questions, or responding to a deluge of links, and suggestions.
(The equation ten seconds to ask a question/ post a link; ten minutes to answer it/ watch a link - makes this a very efficient process of multiplicative time-wasting.)
The Achilles Heel of blogging, which trolls exploit; is the mushy-libertarian idea (to which I have never subscribed) that the blogger has a duty to publish and respond to comments: that a blog is, in essence, a public forum.
Failure to publish and respond to comments is regarded, in some quarters, as 'censorship' (like that was a bad thing) - or un-macho.
For me, a blog is a kind of writing; and comments ought to enhance the reader's experience. And if commenters are bothering me for any reason - then the software can block them.
And when it comes to time-expended deleting versus making comments - the efficiency factor strongly favours the blogger rather than the troll.
...Which is a cheering and motivating thought!