They're not "enabling" a dictatorial regime, they're just following the laws of a foreign government. Making a censored search engine isn't "supporting" the government, it's just abiding by it.

A censored search engine is a direct instrument of oppression.

Contracting to build a censored search engine is the moral equivalent of contracting to build a barbed wire fence around a concentration camp.

You're being an active participant that directly assists in making that oppression happen by building tools required for the actual act of oppression, as opposed to building something that merely done in the same country.

There are over a billion innocent people in China. The products themselves are mostly innocent and the people who build them make their livelihoods manufacturing them. That the government takes a cut is incidental. It's simply not comparable to a product specifically built to support dictatorship.

Over 5 trillion in US tax money has been used to prosecute unjust war in the middle East resulting in 100s of thousands of deaths. Is boycotting Disney movies that support the government through taxes the same as boycotting predator drones?