No you were not thick or brainwashed.
You responded in good faith and that this was progress.
The majority of people are good people and want to see the world in positive terms.
The trouble is that not everyone is like that and some people aren't interested in the well being of others in the same way as those with genuine good faith.
This is a symptom of living in a bubble of having a good life untouched by the reality of bad faith actors. It is the very definition of being privileged that you don't see the negative side of life.
Indeed humans are actually programmed to almost be in a state of denial about risk - its what allows us to explore and push boundaries that other animals wouldn't because of fear. But this has obvious draw backs in certain situations. Many of us would touch the red button labelled 'Danger: do not touch' just to find out what happened.
And critical thinking and joining up the dots between unrelated pieces of information is something that social media actively discourages. Social media is short bursts of information in a condensed form with a lack of depth. People read, feel satisfied that they have educated themselves and know something but don't bother to either check it, read in more depth or challenge themselves with a counter argument. Why? Because people are lazy and this involves effort. We live in a microwave instant gratification world. This actually does something to our brains - we seek out dopamine hits from social media and gaming, with reward instantaneously.
I don't think people are stupid for falling for it by any means. Three word slogans are thought terminating cliches. They are actively designed to stop people thinking. This has been well researched - they know they appeal to our emotional side of the brain which is stronger than our logical side. We have to actively be aware of the propaganda landscape around us. How does advertising affect us. Where is it around us. Its not just people selling us products - its people selling us lifestyles and ideals.
I think this is why this particular issue sells best to the young. Its people who haven't hit the wall of reality that actually not all good faith actors have your best interests at heart. Cynicism is a learned trait from experiences of having been let down despite promises. (By the same token thats why Brexit slogans sold better to an older audience.)
Critical thinking is something you have to work on, practise and value. Its not instantaneous. It can be difficult and challenging. It makes you question things you 'know to be true' and it takes a certain amount of humility to recognise and acknowledge your errors.
Humans are funny things. Sometimes they find belief and idealism comforting because reality is darker and much more disturbing at times. Who wouldn't want to live in a land where we all live happily ever after and there are easily identified black and white heroes and villians?
Its much harder and uncomfortable to realise that things aren't that simple and people who are 'good' are actually flawed and can do things that are hypocritical, naive, and at times actively harmful. Sometimes this is intentional. Sometimes they are just so self absorbed or not capable of empathy due to their neurology that they are completely oblivious to the experience and effect on others. It may or may not be malicious.
Where the state comes in - or is supposed to - is to identify these range of conflicted and assess various harms and their level. And then balance them. This can only happen if you have a range of people from different backgrounds able to speak freely and openly (the real definition of liberal society) to protect everyone as much as possible. And then the media report this as such.
This issue and many others are highlighting institutional failure to do this. Indeed institutions are actively using the knowledge of this dynamic against certain groups to get what they want rather than doing the best for society as a whole. This is ultimately never sustainable as over time it builds resentment and public backlashes as scandals happen. These are hard to repress - even with an increasing authoritarian stance. Even China had a scandal over Wuhan.
Manipulation of good people and trying to silence other is a hallmark of something. Not a good something. Its highly sophisticated and deliberate.
OP take the lesson from this. Critical thinking is a wonderful thing.
en.m.wikipedia.org/wiki/Propaganda_techniques
Read this Wikipedia page on propaganda techniques. Learn them and try and spot them every day in your life. It will make you see the world in a completely different way if you can readily identify them.
I think it should be compulsory learning for all children in the 11 - 14 age group. Its essential to know to navigate the world well.