That's not jut tangential to the point (whataboutism?), it's what every country does. The UK has a better negotiating position than Britain would have. The EU(28) would have a better geopolitical posture (thanks to UK's military, as the EU has a hard power problem) than the EU(27) will have. Geopolitics is highly competitive and mostly zero-sum, which is why you have "unethical" behavior like that.