The trouble is, now it WILL be harder for you to find a job later. These policies are “your choice” like a diabetic taking insulin “chooses” to take insulin. If we actually treat things like this as a choice, the word loses all meaning.

My job hunting days are long over but you're right, LinkedIn et al are indulging in a form of blackmail with chicanery like this.

Having said that, I've noticed most resumes I receive have GitHub links over LinkedIn. We've advertised on LinkedIn with mixed results, employee referrals have always been more effective.