Is it acceptable to climb a popular route without a rope while others are around?

The presence of others changes it, and the reason is that the risk is not entirely self-contained, which is where the personal-autonomy argument runs out.

What gets externalised:

• The people who would have to respond. A serious accident at a busy crag means bystanders performing first aid, and rescuers taking on real risk to reach the site. Neither group consented.
• The people who watched. Witnessing a severe accident is not a neutral event and it stays with people.
• Access. Serious incidents at popular venues have historically led to closures, restrictions and liability disputes for everybody who uses that crag.

None of that means the activity is illegitimate. It means "my risk, my choice" is an incomplete description of the situation, and the objection you heard was probably about the incompleteness rather than about the choice.

There is also a practical dimension separate from the ethics, and it may be what actually annoyed the other party.

On a busy route, climbing without a rope means somebody moving through a space where ropes, other climbers and dropped gear are present. That is a genuine hazard to the unroped climber — a swinging rope or a dropped belay device is trivial to a roped climber and not to someone with no margin.

And it works the other way. Other parties may feel unable to climb normally, unwilling to lower, reluctant to shout, because of who is above or below them. That is a real imposition on how they use a shared venue, regardless of anybody's philosophy.

Most of the experienced climbers I know are relaxed about this activity in principle and would rather it happened somewhere without an audience or a queue — for the practical reasons as much as the ethical ones.

It is worth resisting the framing that this is an unusually reckless thing that other climbing is not, because that framing does not survive contact with the sport.

Moving unroped on easier ground is routine in mountaineering, where the terrain is less technical and the exposure is greater. Plenty of accepted practice carries substantial risk. The line people draw is not really about roped versus unroped; it is about competence relative to the difficulty, and about margin.

Which points at the question worth asking instead of the categorical one: is the person operating well within their ability, on terrain they know, in conditions they have assessed? A climber on ground far below their limit is making a different decision from one at their limit, even though both are unroped.

That distinction usually explains why experienced climbers react calmly to some instances and badly to others.

On the group dynamics, since this started as a disagreement among friends: the thing worth being careful about is the effect on newer climbers watching.

Risk normalises through observation. Somebody two months into the sport who sees a respected friend doing this is receiving information about what is normal, and they are the least equipped to evaluate it.

That is not a reason to forbid anything. It is a reason for the person doing it to be conscious of who is present, which is a smaller ask than the argument you were having.