Disagreement becomes dangerous when the relationship is forced to prove itself during every difference.

In a solid relationship a disagreement is just a disagreement. In a fragile one, every difference becomes a referendum on whether the whole thing survives, and both people start arguing about the relationship instead of the actual subject. The stakes get inflated until nothing small can be discussed.

If ordinary differences feel dangerous, the problem is likely the underlying security rather than the topics. Say that out loud. Establishing that you are not leaving over this makes it possible to actually talk about the thing itself.