How to trick somebody that does the Fromm Gambit into playing a 1.) e4 e5 opening

1.) f4 e5

2.) e4!

1 f4? e5? 2 e4?
1 f4? is inferior to 1 e4 or 1 d4: it does not develop any piece and it weakens the king's side
1...e5? is an unsound gambit: loses a central pawn for no real compensation
2 e4? is a missed win: 2 fxe5 and returns to a dubious gambit ("loses by force" - Fischer "I did not find a way for white to equalise" - Kramnik)

Not exactly a trick... transposing to the king's gambit is one of the main options.

#5
And Kramnik incorrect too?
Loses by force deserves a single ?
Loses a winning position deserves ??
1 f4 does not deserve ? it is probably still a draw.

#8
So the choice is between a slightly worse endgame 2 e4? and a won endgame 2 fxe5.

What is a slightly worse endgame? Is it a loss or a draw?

#9
That is sense.
?! and !? is rubbish. Is it good or is it bad? It is nonsense or lazyness.

#13
!? and ?! have been used in the pre-engine era and by lesser annotators.
If you trust engines that much:
1 f4 -0.3 so still a draw
1...e5? +0.7 so a loss for black
2 e4? -0.5 so maybe a draw, maybe a loss for white

#16
There is no current theoretical standing on the Fromm Gambit:
Larsen was the last GM to regularly open 1 f4
Carlsen has occasionally opened 1 f4
Nobody nowadays plays 1...e5?
Lasker did in his time.
So per GM Kaufmann the +0.7 means a loss for black.
A choice between -0.3 and +0.7 is clear.
A choice between +0.7 and -0.5 is clear.

A) 1.f4 is a good move.

B) 1...e5 AKA From's gambit, is a very good answer to it- actually one of the best Black gambits, used regularly by several Grandmasters.

C) 2.e4 is a King's gambit, which certainly does not lose for white.

D) You say nonsense all the time, although this could be omitted as self-evident.

For the record: great openings expert GM Mihai Marin won a tournament recently playing as white 1.f4 exclusively, and he has been playing the move very frequently for the last 4 years or so. I think there is a very slight chance he knows better than you do, no?

He has even authored a course on 1.f4 where he considers all reasonable black replies to it... I think not 1.f4 b5, which was played against him by Alexey Shirov (Black won quickly after a serious error by White).

#18
A) 1 f4 -0.3 is probably the same as 1 e4 or 1 d4 at +0.3: a draw
What tournament of Marin do you talk about? Benasque Open 2019?
An open tournament is all about beating the weak and the opening does not matter.
https://www.chessgames.com/perl/chessgame?gid=2113846  
AlphaZero ranks 1 f4 as #13 of the 20 possible first moves, behind 1 a3 and 1 h3.
See figure 31
https://arxiv.org/pdf/2111.09259.pdf 

B) 1...e5? is just bad, loses a central pawn for no real compensation.
There is no objective reason to prefer 1...e5? +0.7 over -0.3 1...d5.
How many opponents of Marin played 1...e5?

C) Maybe white can hold a draw with effort after 3 e4. There is no objective reason to prefer 3 e4? -0.5 over 3 fxe5 +0.7 a probably win.

D) I say sense all the time, some fail to see that.

No. It was a tournament in Romania.

The first tournament he decided opening ALL his white games with 1.f4 was the Porto Mannu Open 2019 in Sardinia, where he won 3 games, and lost one (against former WC GM Anna Ushenina).

And 1.f4 e5!? 2.fxe5 d6 "loses a central pawn" for a very good reason: white's kingside is weakened, and the d6 bishop is ideally posted to take advantage (leaving aside that Black has already catched up in development, plus some).

I had the impression that (1.f4 e5 2.fxe5 d6 3.exd6 Bxd6 4.Nf3) 4...g5 is not sound, and Black has to handle this positionally with 4...Nf6 etc, but actually both moves are OK and giving Black sufficient compensation for the pawn.