Explain the irony of Macbeth's seeming indifference to Fleance. Is he really unconcerned with whether Fleance dies or not? Explain.( Act 3)

I see no indifference on Macbeth's part to wheter or not
he wants Fleance dead. Every time Macbeth mentions Fleance, he sees him as a threat and
wants him killed.

Here in act 3, scene one, he speaks to
the Banquo. He is planning the murder of both of them and wants to make sure that
Fleance will be with his father:

readability="12">

MACBETH:We hear our bloody cousins are bestow'd
In England and in Ireland, not confessingTheir cruel parricide, filling their hearers
With strange invention. But of that tomorrow,When therewithal we shall have cause of
stateCraving us jointly.                  Hie you to horse; adieu,Till you return at
night. Goes Fleance with
you?

Here, in the same scene,
he tells the murders that it is just as important to kill Fleance as it is for them to
kill Banquo:

readability="9">

MACBETH: ...To leave no rubs nor botches in the
work— Fleance his son, that keeps him company, Whose absence is no less material to me
Than is his father's, must embrace the fate Of that dark
hour.

Also in scene 3,
Macbeth tells Lady Macbeth of his desire to kill both the father and the
son:

readability="11">

MACBETH:O, full of scorpions is my mind, dear
wife! Thou know'st that Banquo and his Fleance lives.

LADY
MACBETH:But in them nature's copy's not
eterne.

MACBETH:There's comfort yet; they are
assailable.

And in scene 4,
we can see how upset Macbeth is that Fleance has escaped and how he continues to want
him dead:

readability="26">

MURDERER:My lord, his throat is cut; that I did
for him.

MACBETH:Thou art the best o’ the cut-throats! Yet
he's goodThat did the like for Fleance. If thou didst it,Thou art the
nonpareil.

MURDERER:Most royal sir,Fleance is
'scaped.

MACBETH:Then comes my fit again: I had else been
perfect,Whole as the marble, founded as the rock,As broad and general as the casing air:
But now I am cabin'd, cribb'd, confined, bound in To saucy doubts and fears.—But
Banquo's safe?

MACBETH:Thanks for that.                    
    There the grown serpent lies; the worm that's fled Hath nature that in time will
venom breed No teeth for the
present.

Oh, no: there is
never a doubt as to Macbeth's intentions in regard to Fleance... no room for
irony.