a) it’s quite common, so a lot of people have encountered it

b) feet are rather dirty, so it evokes disgust in those that don’t have it

This creates an environment in which people can commiserate in their disgust with others by means of insult. This creates a meme that people will take on as a belief to join the in-group / avoid being targeted by the majority.

It’s the same as a lot of arbitrary hate, honestly.

Dopamine does a lot of things. It does not cross the blood-brain barrier.

So taking this would be all side effects and no benefits

It is conceivable that the glue was put there for another purpose, and the pigeons simply landed in it. That’s just not likely in this case

Disclaimer: I have no experience with this drug class, and my medical knowledge is that of a novice.

“Don’t expose it to light” typically means “don’t leave it in the sun too long.”

These warnings usually mean that the chemical will denature / break down when exposed to light or heat which leads to a decrease in efficacy. Most chemicals will only do this in response to IR or UV light. If the reaction is from IR, then the primary worry is keeping it cool enough. By the nature of indoor lights, your bathroom light is almost certainly not emitting enough UV to cause a reaction.

If the drug is colored (I don’t believe this to be the case here), then visible light could cause a reaction, though I would still find it unlikely that a drug would lose sufficient efficacy due to a bathroom light.

I wouldn’t worry unless it got too warm for too long.

I can’t say anything about the label turning red without a bit more info about the container itself (is it just a vial?), but it sounds like it might be an indicator that you took your last dose.

As always, contact your doctor or provider if you have concerns.