Sounds like this new Necron player may have an attitude problem, but I wouldn't be too scared of his army. There is no such thing as a "cheesy" or "beardy" army list in 40K. And this is quadruply true for the poor Necrons. If this guy, regardless of attitude, is consistently winning with them, then he's got a solid handle on 40K and should at least be respected for the quality of his play. "Destroyer wing" or not, Necrons suck. To win with them these days requires considerable skill. (Or terribad opponents! :rotfl: )
If this guy is taking "max" Destroyers, then the minimum of his army is
HQ
[170 pts] Destroyer Lord, res orb (I assume res orb, it could be nothing or other stuff entirely)
Troop
[180 pts] 10 Warriors
[180 pts] 10 Warriors
Fast Attack
[250 pts] 5 Destroyers
[250 pts] 5 Destroyers
[250 pts] 5 Destroyers
Heavy Support
[195 pts] 3 Heavy Destroyers
[195 pts] 3 Heavy Destroyers
[195 pts] 3 Heavy Destroyers
Total: 1865 pts
So 135 pts for trimmings to fill out 2000 pts. But nothing that would alter how this list would function.
Firstly, that is a damn respectable amount of firepower. And it's fast, mobile, and long-ranged. Necrons may suck as an army, but you must at least acknowledge the strengths where they exist. 45 Str 6 shots and 9 Str 9 shots aren't too bad. The army's also got at least 20-40 Str 4 shots plus whatever else can be had for 135 pts. That said, most of those Str 4 shots probably won't get used because Necrons can't afford to put Warriors into offensive (i.e., dangerous and risky) positions. They will rarely get employed as anything but phase-out prevention and last-minute objective holding.
Let's compare to the 2000 pts Tau list I play.
* 10-20 Str 6 shots (plus 2 Str 6 large blasts if required)
* 20 Str 7 shots
* 2-4 Str 10 shots (depending on use of hammerhead railguns)
* 2-4 Str 8 melta shots (piranhas, depends on how many pathfinder units I use)
* 20-40 Str 4 shots (Kroot)
* lots of Str 5 (from everything else)
What I see is relative parity on the long-range shooting as far as raw numbers. However, Tau far exceed the Necron's ability to pump out AP 1/2 shooting and also have a lot more basic anti-infantry firepower than Necrons. Tau also have credible assault threats in the form of Kroot. (It's not like this Necron army can fight!) And Tau are no slouches on the mobility front, either, if not quite as fast as this particular Necron build. (However, if this person is moving more than 12" a turn he's not shooting. Win for you!)
Clearly, the Tau must be considered the better army in this matchup. You have better shooting, mobility is at least equal (though I would argue that Necrons have to play keep away in this matchup, letting Tau be an aggressor for once!), and you have stronger assaults, too. Tau also have units they can afford to throw away. Necrons do not.
No matter which way you look at it, Necrons should lose this game. Theoretically, at least. Again, if this particular player is very skilled, you will likewise have to be skilled in order to turn your inherent advantages into victory.
Harass those destroyers with your piranhas. Put all your shooting into them until you wipe entire units, thus denying WBB. Focus on one unit at a time. Don't stop shooting at that one unit until you have knocked out each and every model in it. Only then move on to the next unit. Infiltrate the Kroot to limit where they can jet to to avoid assault. Make them waste shots on your Kroot rather than your battlesuits. This is one of those rare games where you don't need to castle, and probably shouldn't. You still need to provide cover for your suits, but that's what devilfish and hammerheads are for, right?
Good luck! Don't be intimidated by this guy or his army. It's a fragile army, more fragile than yours. Stay calm and focused, and aggressive, and you should be OK.