This screams of a young adult with no direction, purpose, healthy interests. The devil makes work for idle hands - he is hitting back due to an obvious lack of boundaries and he hasn't grown up and developed any sense of responsibility or respect, whether than has been through issues or lack of mentoring and guidance in his formative teen years or he is just a lazy shit is irrelevant a baying mob mentality with an "easy" solution to kick him out without knowing the details of his life is not helpful for you and potentially dangerous for him.
Explain to him calmly the rules of the house going forward. You love him and he always has a safe home with you but he is expected to be respectful within it. He contributes £xx amount (most of his benefits), he contributes to housework, he eats family meals etc, he shows respect in the house - no loud music, is quiet if coming in late etc. If he plays loud music go into his room and do not leave until he turns it down, stay calm even if he kicks off. If he doesn't contribute to housework don't do anything for him - no lifts, meals made, laundry done with family laundry, don't take in parcels, change internet password.
Spend time with him and talk about what support he needs to find work, get a purpose and get out of the rut he is in, his self esteem and confidence will be at an all time low and he will need your help with getting back on track more than he ever needed you before as a child. If he wants money he need to be applying for every entry level job vacancy he can find - nightshifts shelf stacking in retail, fast food, labourer, just to get a purpose and experience. There is something out there for him, it will be harder with no experience yet but he needs to keep trying until he finds someone who will give him a chance. The only jobs I would not expect him to apply for would be carer type roles unless he is suited to them as the stakes are too high there if he gets it wrong.
Yes he is 21, he is an adult, but for whatever reason is hasn't been a successful launch and you need to put in the hard work to support him with this before it is too late.