On point you are correct; Thailand has the right to pass laws and enforce said laws.
However, it is not "besides the point" with regards to those laws making sense or not. Laws must make sense. Now, whether or not 'we' (Farangs) see that sense and not just the usual Thai lack of making sense is another issue all together.
Furthermore, There is a good deal that 'we' can do about it. We can complain, in a loud voice... with a somewhat fake smile on our faces, Yell at our Embassies, Write letters to everyone repeatedly. Do something, rather than just bending over and saying "Please sir, can I have another".
To simply "except" the nonsense that these new Immigration rules are demanding from us (except for those who are Chinese, and/or are what the Vegas Casinos call "Whales") and playing 'dead' and 'rolling over' is not a norm that any of us from the West know how to do with any great capability (the France and the US would be first on my list... followed Australia and then by the UK ... albeit with latter's usual Stiff Upper Lip).
Those with Thai children (their own or those that they have 'accepted as their own') who have been here for years, these rules will eventually push them out and in so doing break up the all important Thai family unit. Not to mention separating the father from his children (have you seen how difficult it is to get Visa for ones Thai children into the EU, US, Australia, etc?).
Also remember that with every foreigner that leaves, a part of the Thai economy leaves with him! For example (though not exclusively) , gone are the school payments, the Tops or Tesco's shopping bills, the car payments to the bank, and a slew of other financial responsibilities that upon his leaving will fall directly into the lap of the Thai family... moral or not. Oh, and let us not forget the medical payments for the grandparents house, utility bills, etc (I will leave the 'sick cow' out of it).
So I ask... Thai immigration, is this a good thing? That is the question you should be asking! For it is backward thinking, without a shred of Common Sense or Logic. You are shooting yourselves in the foot... with a 12 gauge shot gun!
But this is Thailand. Somewhat of a new one. One that thinks it is better than everyone/everywhere else and being the seat for ASEAN this year... and power brokers ruling the show... what do you expect.
As for "except it or leave"... yes.... that is an option. But again I ask you, what about the families, the children and the rest as mentioned above.
It is easy to say "leave" but it another thing to actually do it without hurting those that you love and families that you have built or accepted as your own and been with for year upon year without breaking any laws and being a 'good neighbor'. To those that say "leave" perhaps you are right and we all should. Vietnam is beautiful and cheaper and a 12 month Visa is only $135 (multi-entry). But to leave because of stupidity and non-rational thought of the present government here... is not right. It is not right for their own people who have lives and children and who will be or have a very good chance of being put into hard times if 'we' leave.
Don't agree with me or do... that is up to you. All I ask is that you think about it and understand that there is a far greater negative impact than what at first glance is visible.