The arguments are that “Lucy in the Sky with Diamonds” has LSD in the title, but it actually is LITSWD. And that Lennon was lying for no good reasons. And i am not the only one- most posters here agree it is not about drugs.
Wikipedia disagrees.
This cite disagrees-
as does this
and finally Snopes
and yes, Lennon and the crew could be coy and joke around, but Lennon was interviewed many times about the song and steadfastly, every single time denied it was about drugs- while cheerfully admitting other songs were.
Thank you.