Trolling can sometimes be gaslighting, but I think there are posters who would not be considered trolls under MN definitions, but who gaslight on the forum. I don't think one has to be in a personal relationship with a person for them to gaslight us.
The idea that women are over emotional is a prejudice, but it is a characterization that women internalize - and it can therefore be used as a tool with which to gaslight them.
I think constantly saying to a feminist or a group of feminists that the reason they think what they do, is because they are damaged goods, victims, man hating, etc. is a form of gaslighting.
It is trying to make people doubt their rationality and their views, not by engaging with the views and deconstructing them, but by suggesting that the holder of the views is not quite the full shilling, is not to be taken seriously or, listened to. Indeed rational, healthy balanced people might want to distance themselves from such people and their views.....
It is a manipulative mechanism that is used against feminism all the time - most of us can spot it a mile off.
Sometimes it is done by saying that feminists are taking things too seriously, that they can't take a joke, that they take offence at everything. The point is to gaslight the feminist but in order to influence a third party not necessarily the feminist herself (although she may being to doubt herself too). Hence why I call it 'group gaslighting'. The less stupid MRAs sometimes do it.
When the feminist objects to this behaviour she is then told that she is insane/humourless/overreacting/aggressive/a meany/rude/abrasive/shrill/rabid/extreme/etc. In other words, she has just confirmed what the gaslighter said in the first place - she is emotional and unreasonable. The underlying sentiment being that her views and ideas are hooey and that the gaslighter can disregard them.
It is a classic gaslighting pattern. It happens all the time here.