Is it? The flag is black, so could be a variety of things, not necessarily even a national flag. Just a flag in a march. (Anarchism uses a black flag.)
The guy is walking off a cliff and he is blinded by the flag. I assume it is a commentary on Brexit. It is just short of a decade since that vote. Nationalism blinded people and they did something stupid. Not dissimilar to what is going on in the US too.
And how is blindly following a flag differ between a national flag and an ideology flag?