Sorry, but you're either oblivious or just didn't look at the exact series of events.
Just to remind (also, sorry for not-too-good english):
So-called euro-maidan started November 21st. Up to November 29th, it was about signing the association agreement.
Then, at November 30th, it was declared that the square should be decorated for Christmas. Decorators were accompanied by special police force and, well, things get down from there. As far as my knowledge goes, this Wiki article is more or less correct about further events.
Now about motivations. There was significant (I'm not saying "justified", but significant for people who went against the government) fear that there wouldn't be any fair elections. Not long before, Vradiivka incident occurred (long story short, there was a rape with the accused being protected by different officials that were supposed to be objective; this Wiki article contains a brief summary). So there was, and still is, strong distrust in any official institutions. People didn't trust President who said there will be actual, honest elections, people didn't trust any court that could declare whether there was or wasn't any cheating and people didn't trust police that should prevent that cheating.
Systematic episodes of what seemed to be corruption and non-fair play undermined citizen trust in President to a degree where they simply didn't see any other way to prevent him from doing as he pleased (and as would contradict their interests).
It is up to debate whether this was against an ideal of democracy or the legitimate "right to riot". And if we go with the latter, suppressing other protesters going for different cause can indeed seem hypocrite. But, in the end, it is about question "when people have the right to break the law", which, for obvious reasons, can't be formalized and put into a law itself.