So, all it takes for an attacker to "paralyse" Bitcoin is to takeover major miners and set them to ignore transactions?
You would need 50% of all miners and thats alot to increase the average confirmation time from 10minutes to 20minutes. That doesn't really sound like a threat does it?
There's no financial interest in doing so and humans usually follow their financial interest. Even if you could get 50% to not include transactions, fees would increase and therefore more ppl would start including transactions again instead of losing money.