There's NOTHING wrong with being a partner and taking legal steps. This is the shame of the tube site, Not the Content Owner.
Sending DMCA and keeping your illegal content from the tubes is Not threatening and tubes should Not feel like you describe. This is a 100% legit and normal thing to do, if they 'kick you out' from the Content Partner program for this than they STILL HAVE to remove your content which is illegally there and than they will make no money on your content anymore [at least not legally]. So in my eyes this sounds ridiculous...
I believe 3-4 days is a lot if it is about taking down your content. It should have been done in a Few Hours
and I don't see why should anyone wait with it because of holidays, whatsoever... If someone would put your watermark on n underage video and upload it, you would understand what I say immediately. Not saying this could happen or if this is a common habit, but Content Complaints should be handled immediately, 365 days a year
Such big tubes with huge budgets should not complain about doing this the right way..
Your last sentence made me believe you think that tubes are the Kings of this industry and they do you a favor when they send you this affiliate traffic. Actually, while some tubes force you to a deal to get the very last pieces of traffic [watermarking] out of your content they make fortune on the ads on your video pages which you get 0 from. I am not sure about the numbers, but while you have a video on a big tube, get 1m views, you make for example 3-10 sales on banners/links [usually half of it is yours, but you have to cover all content related costs], maybe one more on the watermark traffic [usually 100% yours] while they make multiple times more on their own [sharing 0% with you] on the traffic from popunder(s) and all kinds of other ads on the video page With Your Content... O yes, they need to cover bw costs.. which is peanuts imo if you related it to the income.