You're treating the symptoms without treating the underlying problem.
The majority of the playerbase finds raiding to be too hard, un-fun and/or just plain not worth it.
While I'm sure you disagree with that, and I'm inclined to agree with you as far as raiding being "too hard", there is nothing you can say that will convince me that raiding is "fun". I've raided in the past (back when M-24s were king) and did ok -- but I didn't enjoy it -- so I stopped and haven't raided since. Furthermore the current "rewards" for raiding are pure and utter garbage imho.
Thus I don't raid. Forcibly removing my White Flag isn't going to make me raid. At best I'd endure the attacks (unlikely to get many as a pacifist task based alliance usually scoring 0 points). At worst I'd quit the alliance so I could put the White Flag back on.
But that's just me.
Less than 2% of the playerbase actively raids. That speaks volumes as to what the majority of the playerbase thinks about raiding (they hate it).
You should be coming up with ways to make raiding fun for the 98% of the playerbase that currently doesn't raid with tangible rewards that make it worthwhile.
Forced removal of the White Flag is just going to harden peoples existing opinions.
This is exactly what me and most players I have been discussing with are saying: Raiding is hard, not fun until you painfully learn the basics and the rewards can not even out thos disadvantages.
I am in an alliance using WF. Playing the war tasks and enjoying the boosts really adds to the fun of the game to me. Not having the possibility to play the alliance with WF would be a real loss of fun in the game.
And from time to time I remove WF for a war round and raid for a war reward box. I do this even for the price of getting hammered by the uni-lr-ally-kings on and on ... but as long I know I can put on WF at the end of the war round and relax for the coming rounds thats ok with me. So WF keeps me in the alliance and available as a war target at least sometimes. Without alliance and WF I am out.
Also I spent real money to buy WF. I would be very disappointed from the Devs if the use I bought it for would be removed.
Love this game! WF must stay as it is! Con & Devs you are running a great game ... the recent updates (island, crafting, infamous items, bounty boxes +++) are great!