Do you agree with the speaker's feeling in "A Poison Tree"?

The speaker in the poem "A Poison Tree" describes what happens if anger is left to grow, unchecked, and without reconciliation. In the first stanza, he says that an anger which is dealt with and discussed will come to an end because it is dealt with straight away. By contrast, an anger which is not spoken or addressed but left to grow and grow will grow into something poisonous and fatal. That something in this poem is the apple, which, at the end of the poem, results in the dead body of the speaker's enemy.
This seems to be a sentiment that is rather easy to agree with. One need only examine one's own life to realize that when we deal with emotions openly and honestly, they tend to resolve themselves more easily than if we allow them to fester and to go unspoken. If you have an argument with a loved one, for example, you have two choices. You can talk to that loved one, explain honestly and calmly why you are angry, and try to reconcile with them. And the chances are, if you take this approach, you will achieve reconciliation, and the anger will subside. Or you can let the anger from that argument go unspoken, perhaps because of pride, and then over time it will grow until it can no longer be resolved quite so easily. At this point, the anger becomes bigger, harder, and, metaphorically speaking, poisonous.