"Trolling" is the practice of sending or posting obviously offensive comments, brutally untruthful statements or words and phrases that we all know to be those that would instigate a fight if stated in the local tavern.
In these situations you need to not become involved. Pass up any urge to communicate with those that do not have the same level of maturity and ethical behavior as you do. If you know you will not be able to communicate with clarity based on an exchange of ideas without degrading to name calling and personal insults – click away, leave, find other like minds to spend your time with.
It is not your job to show these type of individuals the light, or try to change their opinion. Sometimes it is best to just walk away when conversations degrade and mature discussions are no longer possible. With onliners that behave in a rude or immature manner, keep in mind their mission is to annoy you no matter what your opinion is. There are those out there where no matter what you do or what you say you just cannot win. So just move on and find others with like interests to communicate with.
Healthy, constructive conversations are one of the neato parts of being online and give us exposure to new ideas and different points of view. Part of participating online is that there will be times that you will get email from others who may not be happy with something you said, have a difference of opinion or who are simply misinformed. Reply with understanding and courtesy and know that not everyone will have the same ideas as you do all the time and there is nothing wrong with that!
If unfortunately, you do get harassed or threatened, do not hesitate to send a copy of the offending email to the sender’s ISP. Report ongoing threatening or abusive email to abuse@theirISP.com (i.e. email@example.com = firstname.lastname@example.org). The email address "abuse@" is generally the address used by ISPs to send threatening or offensive emails to.