I've never heard it described in those terms. It seems to crop up fairly frequently in areas such as feminism, "social justice", or atheism - topics which are frequently discussed online, which have vocal opponents that repeat certain arguments, and where the opponents tend to use certain rhetorical techniques in arguing.
See, for example, "Derailing for Dummies": http://www.derailingfordummies.com/
As well as a counterargument: https://feministrag.wordpress.com/2012/09/24/derailing-for-d...
"Railing" is necessarily context dependent. Using this particular article as an example, the "agenda" is women's issues in the tech industry in the USA (and, presumably, other developed countries). I suspect it would be interpreted as derailing, for example, to remark that women in the USA are (speaking in a worldwide context) relatively very privileged over many people in the third world, both men and women.
Ultimately, a conversation requires two parties. If someone is speaking over you and doesn't want to hear what you have to say because of their agenda, or their anger, or whatever, that's not a conversation, it's a lecture. They might be speaking on an important topic, or transmitting important information, but no one should pretend it's a dialogue.
If it's twitter, or blogs, or similar, you might as well just withdraw. In fact, you see people do this all the time - back away from conversations when they realize that the other party does not consider it a dialogue but only a means for them to transmit their own 'perfect' opinions to other people.