"Lighten up"

Don't overtly "defend" Amy. (Or Chuck, or any teamaker of any gender, for that matter.) Don't use the word "sexism", don't start doing math on how often each team member has been asked to make tea in the last two years, and don't otherwise call attention to your noble sacrifice (which, as you've seen, in an otherwise-mostly-male crowd serves to throw an uncomfortable spotlight on Amy). Say as little as possible. Just make tea. Try to win the initiative: If you start the job first, it can pre-empt argument over who is going to do it. Or if you lose the initiative, but Amy has interrupted her typing to start making the tea, say something like "hey, if you'd like to keep writing I'll make the tea today". (If she says no, don't press.)

If you inadvertently attract too much attention, you can make a joke about how much you enjoy tea. Quote some Hitchhiker's Guide or something. It's amazing how useful random whimsy can be.

Now, of course if you're always missing from the start of every key meeting because you're making tea the folks in the meeting may be liable to demote you in their minds. This is a sad but true fact of politics: Act like the doormat, and you'll become the doormat. There is a reason why badly-gelled teams tend to try and assign lousy jobs to the person with the weakest political position. So this might not be your final move in this game. But you may be in a better strategic position than Amy to negotiate the necessary change (which could be: rotating the tea-making role through the team, getting catered tea, moving an electric kettle into the corner of the conference room, or just "forgetting" to make the tea and seeing what happens: Maybe the team will settle on one of the above alternatives, or maybe it'll turn out that tea just isn't important enough after all to be worth the risk of introducing hierarchy into an otherwise egalitarian team.)

Luckily, you were close friends. This makes things much easier. This lends weight to my worry about sticking up for other people when they show no signs of bother. Should I have been offended for Amy? I don't know her. As you pointed out, if I did, that would be just as sexist.

Let's be clear here, I'd probably feel uncomfortable for the person being denigrated in such a manner. But what is my responsibility?

I mention this because all to often people are quick to say "Hey, I'd jump in to defend a person," and while well meaning, it's just not that easy. Even women can't agree on this (not that they should). On one hand, Amy was perfectly content and these things didn't bother her. On the other hand, in some manner of speaking, they are still wrong. The move Shallow Hal comes to mind here (to some extent, as ignorance isn't the key part here).

This leads me to my way of thinking. Unless it's out right obvious and offends me, I'm not going to rush to the defense of someone because I think they should be offended. However, I will support people who do come out and clearly state they are offended, and support them. If they accept the treatment (for example, always taking notes at the meeting) without a word, who am I to treat them like a defenseless child incapable of defending themselves.

Supporting the person after they've made it clear they aren't happy with the mistreatment, on the other hand, I think is fair and proper.

Some people might feel awkward raising an alarm that something bothers them. This is understandable. In some manner, we must encourage them without outright saying "Hey, doesn't it bother you that you are always asked to take notes? (Maybe that's acceptable if the relationship is more than a co-worker type)."

In the end, it's the best I can offer.

I'm sure there was a time in my adolescence when the mere appearance of a square inch of uncovered skin would have provoked a sudden involuntary orgasm like some Victorian gentleman, but I have seen enough breasts in enough contexts to realize that very rarely do they imply anything sexual.

For what it's worth, your sources do not support your point. They refer to sexual, erotic and romantic images, which I hope you would agree none of those pictures would be considered.

Sorry about the downvotes, it's a legitimate question to me.

Unfortunately those who can't get over the guilt you feel via this association, are far more likely to defend the same behaviour in others in order to make that feeling go away. This is only going to stop when we stop feeling guilty and choose to act differently.