While there is certainly no need to prove a well known (in context) point there is also no call to be offended by the request. You send children off to do their homework, or read the dictionary.

I also wonder if people with strange ideas about words have ever bothered to learn another language.
Many (most?) languages other than English include a lot of gender specificity in everyday

Certainly not well, which is a good pillar upon which the fundamental ignorance of these people rests. Clueless as to the world, ready to "improve it". Beatings are definitely in order.

It would not be out of line to ask me to prove it if I claimed to be a billionaire, or a rocket scientist or a little green man from mars.

It would be, if you've been in the chan forever and already furnished said proof to everyone's satisfaction, it would be out of line for someone that just stumbled in, and with a request (especially a dumb one like "hey guise how do i scrape websites with this") so therefore a negative value to try and impose his worthlessness (in the sense of, lack of understanding, or better stated, lack of connectivity in the graph that is the understanding of everyone present) upon you, and your own chosen use of time. The correct response to someone walking into -assets and requiring I prove... whatever, that "I'm not breaking the law" or that "I'm not MPOE-PR" will similarly be a bump so they can take some time to rewire their stupid head, read the logs, catch up with everyone else. Because it's their job to do the catching up, much like it's Africa's job to built itself up.

Personally I don’t see why it would matter in an irc chat

It matters immensely, for the following reason : some idiots have decided to get all dramatic if it were mentioned, and so there's a positive value to mentioning it now, deriving from the exact option (in the classical financial sense, it's an option, you get to decide whether x happens or not, this has a positive value throughout its lifetime). Basically the problem here is Lindsay, through her naivite, and the people who are extracting value from her through their evil ideology. Same exact extraction engine as used by the niggers, except applied to [stupid] women, by "feminists".

And since we're on the topic, some Frenchman figured out it'd be a good idea to apply all the pseudoscience and cvasi-statistic that once was applied to meteorologic data spit out "the golfclub pattern" and all the rest of that nonsense : you take 30 years of data, you extrapolate it towards the past (through an interpolation technique designed to beg the question), you then extrapolate this new "data" towards the future, and presto : whatever you want. His name is Piketty and the libtards are loving him.

Now going on to calling this person a lesbian thats over the top. You are insulting all the lezzies out there. Like there is something wrong with liking girls.

Well no. In order to insult someone, you have to say something they wouldn't want to hear. The rest of the world doesn't enter into it in any sense. If some guy thinks there's nothing worse in the world than being an engineer, for whatever bizarre reason of his own, telling him he's totally an engineer is in no way relevant for engineers : they didn't sign off on his bizarre misrepresentation in the first place, and consequently they can't have a stake in its ulterior usage.

So in fact I agree that such foolishness over words is stupid.
But the larger point, that this person was so appalled when asked to prove an identity claim gets lost. It would not be out of line to ask me to prove it if I claimed to be a billionaire, or a rocket scientist or a little green man from mars. Why is it out of line to ask me to prove a gender claim?
Personally I don't see why it would matter in an irc chat channel what gender anyone is, or color or what they had for breakfast but one should be prepared to prove anything like that you wish to make an issue.

Now going on to calling this person a lesbian thats over the top. You are insulting all the lezzies out there. Like there is something wrong with liking girls.

Being a HUman is the only way to power.