1) How do you prove it was the vaccine that caused your side effects? You can't. It's not provable in court because "my legs went numb a day or two after I got the jab" isn't exactly concrete evidence.
2) No company should have their liability removed for any reason, especially by the government. This thinking was partly why the 2008 recession happened. I don't want the government taking on the liability of a multi-billion dollar industry because if the company messes up, we're paying more in taxes - guaranteed - to pay for all the settlements.
3) This mandate by the government violates every part of a right to personal autonomy when it comes to your health - there is a MONUMENTAL difference when the mandate comes from government as opposed to private business. This sets (further) precedence for future governments to give them carte blanche as to peoples' health.
Side note - Just a reminder that government-ran health systems like the NHS makes decisions about your health based on the status of the current system - meaning that people who are too costly to fix/repair/KEEP ALIVE will receive palliative care. That's disgusting to me. (The US healthcare system is a whole other topic entirely, this is just an example of government making bad decisions regarding your health)