100% on the first point but it's not immoral to avoid taxes, it's perfectly good business. If they should be paying more change the tax laws.
Pretty much any and every business needs to move goods or services as part of their operations; requiring a functional road network (funded by taxpayers).
Staff need to travel to the business' premises (or out to customers); also requiring a functional road network (funded by taxpayers).
Factories and offices are protected from looting and damage by the police force (funded by taxpayers).
Fires will be dealt with by the fire brigade (funded by taxpayers).
Staff that become ill will be treated by the NHS (funded by taxpayers).
Many, if not most, staff will have received at least basic education in the country where they're working (funded by taxpayers).
Essentially, the very existence of a business as an entity that can function is heavily reliant on services provided by the state. When a business then abuses financial mechanisms that allow it to legally pay miniscule (or in some cases, zero) tax to the state in which they're making huge profits I absolutely, unequivocally consider that to be immoral.
It's like enjoying a meal with a group of other people, then hiding in the toilets when it comes time to split the bill. The bill still needs to be paid, so now you're forcing others to pick up a larger share of the tab - while you ate for free.
If (and I accept it's probably difficult) those legalised tax avoidance mechanisms could be closed, it would not only make for a more level playing field (because generally these mechanisms appear to only be feasible for large multinationals, not smaller local companies) it would also put - literally - billions of £ back into the tax system.