I think the fact that we don't take their message seriously BECAUSE of their great music is an aspect of their evil. It might seem silly and good but look at the images they're depicting:
"{VERSE 1}
Picture yourself in a boat on a river,
With tangerine trees and marmalade skies.
Somebody calls you, you answer quite slowly,
A girl with kaleidoscope eyes.
Cellophane flowers of yellow and green,
Towering over your head.
Look for the girl with the sun in her eyes,
And she's gone.
{CHORUS}
Lucy in the sky with diamonds,
Lucy in the sky with diamonds,
Lucy in the sky with diamonds,
Ah... Ah...
{VERSE 2}
Follow her down to a bridge by a fountain,
Where rocking horse people eat marshmallow pies.
Everyone smiles as you drift past the flowers,
That grow so incredibly high.
Newspaper taxis appear on the shore,
Waiting to take you away.
Climb in the back with your head in the clouds,
And you're gone.
{CHORUS}
Picture yourself on a train in a station,
With plasticine porters with looking glass ties.
Suddenly someone is there at the turnstile,
The girl with kaleidoscope eyes."
The message of the song tell the listeners to follow a girl named Lucy (Lucifer?) with kaleidoscope eyes, with sun in her eyes, who lives in the sky with Diamonds to a bridge where rocking horse people are eating marshmallow pies and people are smiling at you as you are making this journey. Then it says Newspaper taxis will take you away and to climb in with your head in the clouds (detached from reality?) and closes with plasticine porters (porters are people who carried things back in the days) with looking glass ties and the girl with kaleidoscope eyes waiting at the turnstile (a gate that allows only one person in at a time). If really read that message it seems to be telling us to follow a demonic woman somewhere and glosses over this image with happy descriptions of "cellophane" flowers and people smiling and then it describes people carrying things tied with ties that are looking glasses. I mean that video depicts it pretty well - it certainly seems pretty evil to me. I might be looking more into it than I should because this is my favorite song but the lyrics are very, very strange.