Clearly you never actually knew any contractors, because what you have written is complete bollocks:
"So, your partner gets half the dividends?"
Dividends are taxed at a flat rate no matter who gets them. What you really mean is that contractors would employ their stay at home partner and pay them their tax free allowance to avoid tax/NI on what would now be £6500. However as virtually no-one stays at home and doesn't work these days that is fairly pointless.
"You buy a motorbike on the company and sell it back to yourself at half cost within a year?"
There are rules on selling assets - they have to be sold at a fair value, VAT has to be charged and any under-selling is treated as benefit in kind and taxed. Sure the taxman may not have found these but that is due to them not doing their job properly not the rules being unfair.
"Your business LCD projector is 99% used for watching DVDs?"
Again the taxman should look into these and apply a charge. Not to mention if you buy a big fuck off projector for your business and put it at your home then your house becomes a business premises - this will affect your mortgage, insurance, council tax, incur business rates and such - again it is up to the taxman and local authorities to go after this but them not doing their jobs is unrelated to IR35.
"I do not doubt that contractors need allowances"
Thank you. But we currently don't get them under IR35.
"but the ability to pay dividends on 90% income... and claim every damn thing and then some?"
There are already rules on this - abuse of the rules is, and always has been unlawful and subject to penalty. This is not the result of pre-IR35 and has not actually been resolved due to IR35. Just look at bosses of big businesses - they pay themselves a good screw I admit but they take far more in "other" remunerations - far more tax avoidance there than contractor scum.
"Problem is, ALL the contractors I knew were the bad guys and some still are."
As already pointed out - you obviously have never actually met any contractors, or you certainly have never listened to them anyway. And if contractors still are "the bad guys" then surely IR35 is just an expensive failure and should be scrapped?
Or are you just jealous that you are not good enough to contract and yet you believe the bullshit that contractors spout about earning £100,000 pa and only pay 4% tax? Cos if you actually knew any contractors you would know they tend to big up their income and small down their liabilities - sort of freelance version of pissing up the wall.