Dehumanizing people through racism is a well established method the US has historically used when manufacturing consent to go to war among its people. Look at depictions of Germans and Japanese in WWII. Look at depictions of Koreans, the Vietnamese, Afghans, and Iraqis during the invasions of their countries.
Just because its origins weren't racist doesn't mean it hasn't taken on a racist meaning. Sinophobia is rooted in racism and ignorance.
Taiwan is where the former Republic of China retreated after being defeated by the People's Republic of China. The censorship of Xi=Pooh in China isn't rooted in racism, it's rooted in the political conflicts between the ROC and PRC. China censors these comparisons because they are used by opponents to attack the government. You don't have to agree with their methods to understand why they would want to do this. Censoring realistic threats to the ruling government is a common practice in all nations.
The racist aspect originates from how the meme is used in Western circles where there is a long history of racism towards minorities and the enemies of the US as well as a long history of sinophobia.
If your understanding of history, racism, and their opinions of Trump are so shallow, maybe lurking Lemmygrad to learn why users from this instance act so aggressively towards racism and war-mongering propaganda would be helpful.