I live in Canada. If I can draw a parallel, would my sign be confiscated if it said “Manitoba”?

At the very least, Taiwan is a district/state/province of China. It may also be a country, depending on who you ask, I suppose.

So why did anyone else care enough to have security go and forcibly remove it from that person?

Politics. That’s why.

I bet they’d be fine with someone holding up a sign for “Zhejiang” or “Guangdong” or any other province.

This is stupid.