I heard miner who solved the block can decide to arbitrarily discard some or all transaction from the block. Is that right?
If so, I think someone with great resources can destroy whole bitcoin system anytime if they want it to be happened and there are some people who could actually do that.

Let's check some number first.
7970 GHz has 4300 FP32 GFLOPS and 1080 FP64 GFLOPS and the hashrate of GPU is 0.65GH/s. (which means 1 FP32 GFLOPS = 0.00015GH/s or 1 FP64 GFLOPS = 0.00060GH/s)
2600K has 50 GFLOPS and the hashrate of CPU is 0.02GH/s (which means 1 GFLOPS = 0.0004GH/s)

Judging by above data, 1 GFLOPS can roughly translated into 0.0004GH/s.
Todays network hashrate is 55,000GH/s, therefore 137,500,000 GFLOPS = 137,500 TFLOPS = 137 PFLOPS would be needed to achieve 55TH/s hashrate.
And US Government only has 17.59 + 16.32 + 8.162 + 1.257 + 1.11 + 1.054 + 1.042 (and so on) PFLOPS supercomputers.
So, Now we know that even the US government cannot beat the network's hashrate with current supercomputer especially considering the fact that we are on the verge of ASIC explosion.

However, If someone with great resources try to build their own version of ASIC, It could be very easy to beat the hashrate of entire network by wide margin.
I heard avalon use 110nm lithography, so if someone use 22nm lithography to build their own ASIC, ten fold increase of speed is easy.
If someone develop much better architecture and use 22nm lithography to fabricate much bigger chip, 50x speed bump would not be far fetched idea.

If so, the "improved" chip's hashrate will be 3,150GH/s. 1 million chip means 3,150PH/s which is 63,000 times greater than today's hashrate of entire network.
In other word, he now holds 99.998417% of network hashrate, so he can deny at least 99.998417% of transaction.
If that happen, bitcoin miners and users has two option. Option A, Try to beat him by increasing their hashrate. Option B, Accept the reality and leave.
I think 63,000 times difference cannot be overcome easily, so the most of miner will leave and bitcoin system will be destructed forever.

And i don't think 1 million ASIC's price will be unthinkablely expensive. I don't know nothing about ASIC, but if the die size of ASIC is 400mm^2, you can get 137 of them from one 300mm wafer.
You need minimum 7300 wafer to get one million working chip, and typical 300mm wafer cost $5k-ish, so it's $36.5M.
$36.5M is not little money to average joe, but US DoD's direct spending on Iraq War was at least $757,800M and $36.5M would mean practically nothing for them.

So, Once bitcoin become break certain critical point that could harm the real world economics, "bitcoin is enemy" kinda definition can be made by government.
and since sweep process is relatively easier than real war(find some ASIC gurus, make a $40M worth fabrication deal with intel), destruction will be inevitable.

Long story short, bitcoin will never gain wide market-acceptance because once they do, whole bitcoin system will be wiped into history.
Am i correct or not?