Example:
"People are always criticising the committee system, but if they took the trouble to get involved themselves, they'd be more appreciative of the work being done".
This makes several unfair presumptions (a) that opponents of the commitee system are not appreciative of the work done, (b) that your opponents have never themselves worked diligently on committees (c) that your opponents are criticising individual committee members, when, in fact, what they are criticising is the system itself