If a restaurant throws a black person out for being black, it's not that surprising that people wouldn't be going "yeah but just look at all the black folks they didn't throw out!"
Nobody gets a cookie for not being a dick to trans people. That's just being decent.
I get what you're saying here. Coming from someone who has worked similar customer service jobs, the amount of customer interactions per day for a large company is almost unfathomable to the average person. Someone is almost assuredly going to act against the companies wishes and not get caught. That doesn't excuse the behavior to the slightest.
But I just think that large companies overall "morality" or however you want to phrase it needs to be judged on trends and not isolated situations involving likely 1 person and then customer service who doesn't have the authority to override anything. Judge the person who made the decision sure.
In your example, it's unlikely such a thing could happen without a manager or someone on duty to witness such a thing. So, yes, if it happens if would be fair to judge that restaurant pretty much right away. It's borderline impossible to perform quality assurance on every customer interaction like we are talking about here. It would take a separate person 8 hours to review 8 hours of calls for example and that's why call centers may only QA 5 or so calls out of 1000 per month. I know we aren't talking about calls specifically, I'm just giving you an example from a previous job I had in a similar industry. This is something I know a lot about.
Again, it doesn't excuse it at all. But context has to be considered and it can take a while for these cases to find their way up the chain to correct these types of situations. That's all I'm trying to say.