The Know-It-Alls (Resistansis Futilium)
If the mandolin in the fourth movement of the Seventh Symphony misses a note in the sixteenth bar, these people will notice, let you know they noticed and will attempt to disgrace you for not having noticed. Do not engage them in discussion: it's what they want, they won't even listen to you and you cannot win. Pretend (or not) you have a stomachache and run. They'll let you go as soon as their next victim appears.

The Seen-It-Alls (Prehistoricum Dinosaurus)
These people will try to convince you that you, the unfortunate newbie to Mahler, cannot possibly understand the meaning of real, great Mahlerian performance, since you have never heard a 'live' performance of the Eighth, let alone, for example, Barbirolli do the Ninth with the Berlin Philharmonic in 1964. Don't let them get to you. They will also say the same thing to anyone else, even the conductor, given the opportunity. Unlike the Know-It-Alls, these people are not deliberately trying to be arrogant; they are just mourning their lost years. Smile indulgently and look upon them with as much pity as you can.

The Wannabes (Obscenis Ignoramus)
Conducting one's speakers in the home can be quite fun, but certain enjoyable things done by oneself in private are best left private. When these people wave their arms around in the concert hall, they are merely exhibiting an ungarnished act of self-aggrandizement and the acme of pretentiousness, since if they were any good they would be already up there on the podium and not seated among the hoi polloi. These people have to be shamed publicly at the intermission. You can, for example, suggest loudly mistakes in their conducting ("...sehr langsam merely means very slow, not dead!") or even tell them to "go home and practice some more first".

The "We Came For Mahler" Crowd (Artus Fartus)
Now, these are the people for whom Mahler is more of a religion than an art form, and would rather sprain a muscle or two than admit otherwise. Any reference to his works as "classical music" will elicit violence, tooth and claw, from them. The good thing is that since these people use their nostrils to look at other people who are beneath conversation, they will not bother you much at the intermission. They can sometimes be identified by the battered, oversized Dover scores they carry under their arms.

The "Romantics" (Hypochrondus Maximus)
These people should be avoided at all costs, if only because they are chronically always in a romantic depression (also known as "artistic" depression), despite not really having anything to be depressed about. Readily identified by their black Giordano turtlenecks and constant dramatic wiping of their foreheads with the back of their hands, they are well read, consider themselves poets ("yes, quite, but aren't we all?") and will readily imagine themselves to be suffering (and sometimes dying) from a fatal heart condition, curiously not unlike the one which killed Mahler.

The Evangelists (Zealotum Cultus Mahlerea)
These are people for whom Mahler is absolutely a religion: they are convinced that there is only one composer worth listening to and Mahler is his name. They will feel violated if you even attempt to mention another name in their presence, and have collections of every single Mahler, and only Mahler, recording ever released, plus even more bootleg recordings made on Walkmans and exchanged between themselves. Since the invention of DVD, they will only watch Death in Venice in Soundtrack Only mode. Worse, they will not stop trying to convince you that their religion is the right one, the only one, citing examples ranging from how big Mahler gets ("...and you'll need a cast of over a thousand people !") to how popular Mahler is. There is also a factory beer ad which will send them into paroxysms of ecstasy, especially the portion when the conductor jumps in the air. To them, if there is a composer who could part the Red C, Mahler is him.

Pretend that you have been won over to their faith and have accepted Mahler as the one and only prophet, then try to escape at the first opportunity.

The F.A.M. Syndrome (Kaplaneria Psychosis)
These people suffer from extreme psychosis, also known as the "Fanatic About Mahler" Syndrome. (Also informally called "Flying Around the Maypole", "Foaming At the Mouth", etc.) They will have wet dreams about quitting their jobs, acquiring Mahler's original manuscripts and taking conducting lessons for a whole year, just for the pleasure of conducting a Mahler symphony with orchestras around the world. The extraordinarily wealthy ones, as in "I have so much money I don't even know what to do with what's left with after I've finished spending what I want to spend", have been known to actually make it happen. But such people are, fortunately, very rare indeed.