A quick scansion of the poem confirmed my recall. Iambic TETRAMETER with some trochaic substitutions and an anapest in the line just before the couplet. Whew. Not crazy (not provably crazy anyway). Reading this sonnet again after many years was a pleasurable thing this afternoon. And it is fine indeed to have my thinking about tetrameter upheld at the highest level.
So what to do now about those who would eschew tetrameter? Well, to start with I must promote this meter whenever possible. Keep writing in this most natural of meters. Involve poet friends in use of this metric stance.
And do NOT enter sonnet contests where there is no clear acceptance of the four beat line! Ta Da! Vindication AND a plan!
There may be something more pervasive at work here, however. I worry that in this age of teaching to testing, some students may graduate from high schools and colleges without a broad enough knowledge of the world to actually thrive intellectually IN it. In other words they might not know that they don't know. And do they then reject out of hand anything that points out their lack of knowledge? I saw this in many of my students. It is worrying to say the least.
When I was still teaching in the college classroom, I used a supplemental text to help students "catch up" with what they ought to know about reading in order to understand the way professors want them to read. I am of a mind that every high school student should be given this book upon entering 9th grade and use it through college: How to Read Literature Like a Professor by Thomas C. Foster. The book is a lively read and very helpful for the student who wants to not only know "facts" but how to connect the dots and understand literary and cultural references made in what they read. It is a code-cracking wonder of a book. There are references made to many and varied pieces of literature, and I believe if a reader would simply list all of them and READ all of them, we'd not have such a divide between reading and education.
Now THAT is something to chew upon, reader, something very healthy for your mind to chew upon indeed!