Even without replay protection you can first easily split your coins before starting sending/"claiming" any coins.
Its not like replay attacks are kinda destroying btc. Neither its a danger which comes hidden.
"Replay attack" basically is just to rebroadcast your transaction on the other chain. If you start splitting your coins you start with sending
your more valuable coins (btc in this case) to an address you (and only you) have control of. From now on your BTC are safe. And only this TX can be
rebroadcasted (which is kind of senseless for an attacker to send your bch to an address you own). AFterwards you can start importing your private keys into an BCH wallet.
To not get confused by an "attacker", who is aming for chaos, you then send your BCH to a new address.
Afterwards there is no more risk to an "replay attack".
That's not exactly true in ALL fork situations... it works with BCH because they implemented full 2-way replay protection... but imagine if S2X had gone ahead with no replay protection... you try this and send your coins to yourself thinking, great, now I'm safe... and then send those "split" coins to someone else... Thief then just rebroadcasts the whole chain of transactions (ie. BOTH transactions you've made) and boom, your coins are now gone.
It isn't just a simple case of "send to yourself", it is a LOT more complicated than that... you need to start generating transactions that use inputs which don't exist on the other chain to make it impossible for that transaction to be valid on the other chain. The "easiest" way to achieve that is to get hold of coins that come from a "coinbase" transaction (ie. the block reward, NOT the exchange with the same name)
Splitting coins when there is no replay protection is NOT for the uninformed or technically challenged... it is complicated and exposes you to potential loss of coins on both sides of the fork.
In the case of BCH (and other forks with replay protection)... moving your BTC is not "splitting" them... they're automatically split because of the replay protection. What you're doing is just putting them onto different private keys, so that if the fork wallet you use is "evil" and steals your seed/keys... only your fork coins are at risk.
In this case, having some technical knowledge is pretty much essential for the safety of your coins, because you have to trust that the Electron Cash (or some other software that you choose to download) is safe. While it is open source, it's signed by anonymous developers, so a malicious version could theoretically be introduced. That's why it could potentially be risky to install it on an airgapped PC.
Isn't that the whole point of the Airgapped PC... it doesn't just stop things getting IN... it stops things getting OUT as well?