It's fine to use intuition, but it's extremely important to be able to reflect and recognize on its shortcomings, which is that you may be inadvertently layering your own subjectivity on what you think is objective. In this case your outburst is not valid.
Is forcing yourself on another person immoral? Yes. Is intentionally manipulating someone's relationship for personal gain immoral? Yes. Are two people recognizing they would be happier together, and leaving a previous relationship immoral? That doesn't seem wrong.
You are the one coloring this scenario as "stealing". There is no information here about who these people are, what their relationships are like. You are projecting onto this situation and constructing this strawman, and in turn moralizing about the strawman. That isn't reality.
Is forcing yourself on another person immoral? Yes. Is intentionally manipulating someone's relationship for personal gain immoral? Yes. Are two people recognizing they would be happier together, and leaving a previous relationship immoral? That doesn't seem wrong.
You are the one coloring this scenario as "stealing". There is no information here about who these people are, what their relationships are like. You are projecting onto this situation and constructing this strawman, and in turn moralizing about the strawman. That isn't reality.