No, Instagram should not be censored in China due to pro-democracy protesters, because it is important that the people in these developing countries be able to share their ideas about democracy. These emerging countries are beginning to form their own identities and embrace freedom. It would be to thwart the will of the people to quash their efforts.
I believe that censorship isn't the way to go. China may not be a free country like the United States but you can't start censoring and restricting what the people do on the Internet. If you censor Instagram, then you'll censor something else next and the people may not like it.
Censorship does not make a problem go away. The protests taking place in Hong Kong right now stem from deep seated frustration of the Chinese government. In the past, the government has blocked google and twitter and other sites that give people a tool to connect and strengthen opposition. Take this tool away and the people will only feel more oppressed and rise up.
China has had a history of tightening it's grip on free speech, particularly with internet based services. News of events should always be accessible by anyone at any time, particularly in this day and age. Instagram has been one of the few internet services that's been unrestricted until now, and this cannot be allowed to continue.