I don’t see how this is in contradiction.
To give one perspective of many, Marshall Rosenberg spent his life researching emotions and violence, and from his point of view, anything you do can ultimately be traced back to your own goals. In his view, it’s more useful to allow this idea and explore it, without judging it as negative. Survival/benefit of the group can be your very own personal (long term) goal. For example, a typical tradeoff is your (very own) need to belong, since your survival literally depends on it. No need to see it as either-or; to resolve the inner conflict, one can own both sides of the argument.
Making your emotional state transparent to the group can in that sense again benefit yourself (and the group), but to think that is always the case and that everybody will comply (or even be able to) will lead to disappointment (disillusion), out of principle, since you are installing a moral rule that doesn’t match reality. The verbal sharing of your emotions might successfully (and openly) manipulate the group to include your own goals, and/or the actions you take (taking your emotions into account or not) might.
Note how I am using “manipulation” in its original/neutral form, which means “to move”/influence. Typically, we use the word to convey a judgement - some forms of attempted influence we see as good/acceptable, others we see as negative. But that judgement is based on our own values, and somebody else will have different values. We can see this in how our cultures judge lying (and how that judgement changes over time). Is not sharing all you know a lie (of omission)? Is it acceptable to not always share all your thoughts? In many cultures (families), it is deemed offensive to tell certain truths; there is an expectation to lie! Once there is an expectation, it is not considered manipulation. In some hacker communities, sharing your emotions is considered offensive and an unacceptable attempt of manipulation!
A simplistic perspective which you can check for yourself and compare with others: Anger means you experience something you judge as wrong and possible to influence. Sadness means you experience something you judge as wrong but outside of your sphere of influence. Fear is a judgement of danger. The judgement is real; the situation itself may not actually be dangerous (today). It’s a signal, but it’s not based on reality/facts but your own judgement of it. You can tune the signal and thus your experience by investigating and changing your judgments - without sacrificing any of your needs or goals. Emotional reprogramming takes time, but it’s not outside of your control, nor is it driven by some higher truth than your own judgments, based on your prior experiences.