I'd encourage you to read his argument in full, especially since I have had the privilege of discussing this a few times with Ibish as he's wrestled with his interest in this question.
The literature on The Merchant of Venice is voluminous, of course, so I would like to add a few thoughts on The Jew of Malta.
For me, the prologues (published in their entirety in the Penguin Classics editor of The Complete Plays) are the key to bolstering Ibish's argument that:
Marlowe's play is simply cynical, misanthropic and deeply antireligious. He holds all cultures, civilizations and religious traditions in equal contempt and in that sense, I think it is perfectly impossible to describe the Jew of Malta as anti-Semitic. It's anti-everything.It can't be put much more simply or clearly than in "The Prologue Spoken At Court":
We pursueMachevil, of course, gets his own speech in the actual Prologue to the play proper, and the framing device for the play is laid out quite clearly:
The story of a rich and famous Jew
Who lived in Malta. You shall find him still,
In all his projects, a sound Machevill;
And that's his character.
Albeit the world think Machevil is dead,
Yet was his soul but flown beyond the Alps;
And, now the Guise is dead, is come from France,
To view this land, and frolic with his friends.
To some perhaps my name is odious;
But such as love me, guard me from their tongues,
And let them know that I am Machiavel,
And weigh not men, and therefore not men's words.
Admir'd I am of those that hate me most:
Though some speak openly against my books,
Yet will they read me, and thereby attain
To Peter's chair; and, when they cast me off,
Are poison'd by my climbing followers.
I count religion but a childish toy,
And hold there is no sin but ignorance.
Birds of the air will tell of murders past!
I am asham'd to hear such fooleries.
Many will talk of title to a crown:
What right had Caesar to the empery?
Might first made kings, and laws were then most sure
When, like the Draco's, they were writ in blood.
Hence comes it that a strong-built citadel
Commands much more than letters can import:
Which maxim had Phalaris observ'd,
H'ad never bellow'd, in a brazen bull,
Of great ones' envy: o' the poor petty wights
Let me be envied and not pitied.
But whither am I bound? I come not, I,
To read a lecture here in Britain,
But to present the tragedy of a Jew,
Who smiles to see how full his bags are cramm'd;
Which money was not got without my means.
I crave but this,--grace him as he deserves,
And let him not be entertain'd the worse
Because he favours me.
This is a moral universe turned upside down -- a seething pot of lies, conspiracy and power politics in which nothing is as it seems, where the moral rule of the universe is Machevil's amorality. Those who rule this world speak not of him and keep their knowledge. Those who seem the most religious are, in reality, his greatest adherents. I think these Prologues bolster Ibish's case: The Jew of Malta is not anti-Semitic, but a screed against the common hollowness and hypocrisy of all the Abrahamic faiths.