Is the poet serious about his use of the word "heart" in the poem, "An Apology for Using the Word "Heart" in Too Many Poems"?

There are a number of times of the meaning of “heart” that
might be construed as being not serious or extremely casual and frivolous, perhaps not
serious at all about his apology. The rhymes of “hustle” and “muscle” (lines 7–8), for
example, suggest a lightness of view about the issue, a tone that is maintained by the
phrase “slushily fits” in line 10. The long list of adjectives in lines 12–17,
culminating in “etc.” in line 17, does not indicate great respect for the word. Yet,
after this list, the speaker’s attitude shifts and the remainder of the poem points out
the importance of the word and the need for it. The poem’s last two lines seem totally
serious and earnest.