what is the meaning of “being a screen” here? does it means that “the spiritualists should not allow those villains to present in their sacred ceremonies”?
These fraudulent rascals were sometimes mere cold-blooded swindlers,
and sometimes seem to have been real mediums whose psychic power had
for a time deserted them. There were scandals and exposures, some real
and some pretended. These exposures were then, as now, due often to
the Spiritualists themselves, who strongly objected to their sacred
ceremonies being a screen for the hypocrisies and blasphemies of those
villains who, like human hyenas, tried to make a fraudulent living out
of the dead.
source:http://gutenberg.net.au/ebooks03/0301051h.html _ hos by acd
No, it means that villains were using spiritualist practices as a screen for their own malpractice.
Here screen has the same meaning as blind which Lexico gives as
2 Something designed to conceal one’s real intentions.
‘Ruse’ applies to that which is contrived as a blind for one’s real intentions or for the truth.
In other words they were pretending to be “real spiritualists”, who objected to being impersonated in this way, and were as keen as anybody to expose them.