I'm putting this in the context of Autism, and this is a jaded and cynical answer. I think that those of us on the Autism Spectrum need to be really careful about how we approach this concept of altruism. Sometimes, we want to be nice and help other people, but we go about it in the wrong way and end up angering someone who doesn't want that help, as well as potentially other people who may be involved. The ill-received beneficence draws negative consequences. The feeling of being spurned for having tried to help someone is absolutely dreadful, and is much worse than that of having merely refrained from providing the unwanted help in the first place.
I think that the flip-side is also true: We Autistics sometimes get oppressed with unwanted and unwelcome "help" from Neurotypical people, in spite of what might be good intentions by those people. The "help" can, for instance, take the form of paternalistic interventions in which people try to impose what they think is best for us, against our autonomy and self-determination.
I have a terrible memory from my youth in which I tried to be helpful to a peer, in which I went on and on giving information about something. I had thought that I was just doing the right thing and being helpful. I didn't pick up on any of the non-verbal signals from the peer and from an adult authority figure who was the other person present, that they did not want me to go on talking and giving information. In a terrifying instant, something "snapped": the peer stated a desire to be left alone, and the authority figure suddenly screamed at me full-force in a fit of rage for me to stop immediately and that I was driving the both of them crazy. I was so emotionally crushed and ashamed from this incident, and I can't forget it even to this day. I feel like that enormous scream from the authority figure burned a permanent hole in my very soul. It's a miserable memory. So much for being "altruistic".
Another example is when I helped in a didactic situation. At one time, I thought I was being helpful by giving some information to my constituents. It turned out that I incorrectly judged how much information I should have given out. The authority figure in that didactic situation was infuriated with me, asking me what the hell I was doing, and spewing all sorts of irateness at me. I apologized -- I had to. I thought of resigning from my helper role. I was afraid that I would be formally accused of misconduct. Ultimately, neither of those two things happened, but I live with guilt and shame that I tried to do something right but got it so wrong and drew so much ire.
Remember the saying, "No good deed goes un-punished." Sometimes, less is more. Sometimes, we need to refrain from attempting to be altruistic, because the backlash from doing so can be dire. And, sometimes, people need to refrain from engaging in what they perceive to be altruism towards us. As counterintuitive as it is, altruism is something to be very, very careful of.