How can we be sure an AI doesn't have subjective experience?

It does have, just like us. "Subjective experience" isn't a real thing. A rock also has it. Non-sentient organisms also do.

The thing is, what you perceive as conscience is just a controlled hallucination.

While you are taking a shit, your brain is actually doing a lot of things, but you mostly perceive the input / output, similar to an AI.

We do have emotions, feel pain and other things that AI isn't able to feel, so it doesn't make sense to consider the AI, at the present, as a sentient being.

Also, this is why we humans should accept that for that reason, we deserve to be treated with dignity, so does animals and other sentient beings.

We understand what it means to suffer, we also die and for most of our lives, live very miserable and challenging lives, going through hardship. The AI doesn't.