tempered by fears that...什么意思

that引导的是同位语从句，是可以去掉的，用来解释说明fear这个抽象名词。你可以这样理解：Etaglitarian sentiments were often tempered by fears .
而他们的fear则是the mass of the population was unprepared for self-rule and democracy.
不知道我又没有解释清楚，不懂可以再问。