I get straight to the point.
How would dark eldar react to chaos PC? Normal eldars are easy to predict since they despise chaos in all forms. I was thinking that since dark eldars are rather evil they don't care but will they be willing to talk or deal with chaos followers? How they would react to followers of slanesh, they aren't exactly on good terms from what i know.
I think it just depends on individual Dark Eldar.
For example many Gladiatorial Pit Weapons of Kurse are crude imitations of Dark Eldar close combat weapons, Hydra Gauntlets. Shardnets etc etc. So they must have had somekind of contacts and if memory doesn't fail me some Dark Eldar even frequently visit Kurse for these Gladiatorial combats they have there.
They might make slave trade, much easier to gain already submissive cattle than make raid attack to an Imperial planet.
Dark Eldars might have dealings with followers of Slaanesh but might be more than cautious.
Generally speaking, I don't think Dark Eldars would have many qualms cooperating or dealing with heretics. They only thing I'm sure of is that if you are obviously dedicated or a psyker or anything to that effect, you can forget about anything doing with the webways.
The Dark Eldar (as all Eldar) are incredibly paranoid about daemons infesting the webways, and psykers are pretty much a loophole portal straight into the warp.
So it really depends on what it concerns. They'd probably treat the heretics much like other Mon'keighs.
And if you are marked by Slaanesh in any way, they'd probably treat you like the plague. Some might be immediately hostile, but more likely than anything else, they'd just spit in your general direction and treat you cautiously, calling you pariah and not letting you get close to.. anything. Anything, really.
I don't think you can generalise an entire race like that. You might as well ask how would a human react to Chaos tainted PC's. It depends on the individual.
Some Dark Eldar might immediately think 'Argh! Kill it with fire!' Others might think the PC's to be a valuable resource to be exploited, or a potential threat to be monitored carefully. Of course, some Dark Eldar might not care in the slightest as long as the PC's don't mess with their plans.
In short, I think any given Dark Eldar, or group of Dark Eldar would react however you want them to react to better further your story.
I don't think you can generalise an entire race like that. You might as well ask how would a human react to Chaos tainted PC's. It depends on the individual.
Some Dark Eldar might immediately think 'Argh! Kill it with fire!' Others might think the PC's to be a valuable resource to be exploited, or a potential threat to be monitored carefully. Of course, some Dark Eldar might not care in the slightest as long as the PC's don't mess with their plans.
In short, I think any given Dark Eldar, or group of Dark Eldar would react however you want them to react to better further your story.
Of course you can. Generalising entire races is what fantasy does best. Now, it usually comes down individuals as always, in the end, and personal motivations and so on, but that doesn't mean that there aren't general trends amongst races (or, in some cases, even very strong leanings that cannot be ignored).
How would a Squat react to an Ork?
How would Space Marines react to an Ork?
How would an Ork react to another Ork?
Are Eldar arrogant?
Are humans violent?
Are ratlings lecherous and decadent little space-gypsies that'd steal the hair off your feet if you had any?
Deviations from the norm, just like in reality, is relatively uncommon and noteworthy. It's entirely valid to speculate in how a certain race or culture would react to something generally, or in some cases, specifically.
To make any kind of judgement in this case, though, I think we'd need more parameters. They'd take your slaves, but they wouldn't let you marry their daughter.