I think the examples you give are completely different. Such signs were offensive, discriminatory and unacceptable because they were calling for racial discrimination against groups of people, there's also clearly a nasty intent behind the signs, they are actively discriminating against a group by excluding them.
'Ladies and gentlemen' is a generally recognised polite form of address, it does not have a nasty intent, it is not an instruction to discriminate, or that any group is not allowed on the train. Therefore the suggestion that it's use amounts to rudeness, or someone who uses it is being rude isn't proven, indeed many regard it as perfectly acceptable and completely inoffensive in meaning and intent.
People are of course free to take offence at what ever they like but that doesn't mean everyone has to accept that their taking offence is correct or justified. The idea that because someone takes offence at something, everyone should automatically change in response results in a situation where those most likely to take offence get to dictate to the rest of society, whether justified or not. It puts the opinion of the offended beyond question or scrutiny.