If you have not read Stories Versus Truth, you may want to read that before reading about trolling/bullying.

Bullying is usually just a form of trolling, that is, they troll for Christians as one would troll for fish, with provocative statements or questions but a mind that is totally closed and set on destruction.  Here is a page on how to handle trolling.

An easy way to handle these people is to tell them the truth:

Every evidence that is used against God consists of made-up stories (lies), arbitrary assumptions (lies), or irrational statements (insanity). We have not followed cleverly designed made-up stories, arbitrary assumptions, or irrational statements. Rather, we follow the Living Christ, Who leads us and speaks the Utterances of absolute, genuine fullness of Life to us.

What do you say if they reject Christ and just want to argue?

Whatever they come back with will consist of made-up stories (lies), arbitrary assumptions (lies), or irrational statements (insanity). This is true whether they say "Evolution is science," "There is no God," "God doesn't speak to you," "You are stupid," "You don't understand science," "I don't have enough evidence to believe," "There is no evidence for God," "The Bible has errors," or any other thing, so just say some variation of the following:

Thank you for providing an excellent example: Every evidence that is used against God consists of made-up stories (lies), arbitrary assumptions (lies), or irrational statements (insanity). We have not followed cleverly designed made-up stories, arbitrary assumptions, or irrational statements. Rather, we follow the Living Christ, Who leads us and speaks the Utterances of absolute, genuine fullness of Life to us. (example using this on an blog)

See the baloney detector for more information.