They’re dull, droning, deadly, and dreadful.
They’re didactic, draconian, and dictatorial.
They’re dastardly, dehumanizing, and diabolical.
Doug?
Dude, what a downer. 
delicious
delightful
Do a dance, dig some dirt, dunk a donut for dessert. Draw a daisy that’s D-delightful, and see where D is handy, it’s fine and dandy.
It’s de-lovely!
And without the D, my daughter’s name would be eirre. Makes no sense.
Drill. Drub. Discipline. Demand. Deny. Dominate. Demoralize.
Taking from the thread immediately following this as I opened it, how about Divorce?
Go defenestrate yourself.
And you go dangle your dick in the disposal. 
D’oh! :smack:
How deeply dramatic, darlings!
D words can be depressing, but they aren’t as bad at tinny words…
but the best ones are woody words.
(link goes to the appropriate Monty Python sketch)
Damnation! Yer durn tootin’ dem ‘d’ words are disgusting.
Talk
Talk
It’s only talk
Debates
Discussions
These are words with a D this time
Dialogue
Dualogue
Diatribe
Dissention
Declamation
Double talk
Double talk