On the contrary I don't think anyone is trying to disadvantage me or my children by investing in their own family. Indeed if investing is making them well functioning and productive members of society then that can only advantage everyone. I also don't think anyone is thinking leaving my family money is to maintain and entrench inequality. People don't think like this on the whole.
I don't think that a massive amount of unearned income received by an individual meaning that they can outcompete someone who has worked hard for the money to obtain a scarce asset such as housing is 'investing in a family' though. All it is doing is allocating pre-existing assets based on birth right. There is nothing new able to be done or being produced.
We often hear people saying that they don't want their children working hard like they had to and be able to enjoy life. But then who do they think is going to be doing the work for their children?
Yes life is unfair and if you are on the positive side of that unfairness you will say 'suck it up'. Unless you are an absolute stoic then if you on the negative side of the unfairness you will be a bit miffed and point it out.
As for inheritance tax, I do find the arguments against it a bit ill thought through.
Whilst I might not like the government and think they waste money, the overwhelming majority of government spending goes on pensions, health and education and the issue is in most of these areas not enough money is spent and the decisions on spending in these areas is largely efficient.
The argument that the government is taxing people twice with IHT is just nonsense. The first £325,000 is exempt. Very few people will have actually saved £325,000 through just savings from their earnings. The majority of an estate over £325,000 (if not the majority of any estate) will be based upon property where prices have risen independently of what the person who died paid for it (so just a capital gain) and through investments (again a capital gain).
The person who receives the inheritance does not pay tax on the estate - it is the estate that pays the tax. Even if the person inheriting was the one who pays the tax it is unearned income and I cannot see a logical reason why unearned income should be taxed differently to earned income (well, I can see a logical reason why it should be taxed higher than earned income but certainly not lower).
I don't see a lot of evidence that entrenching inequality through resource allocation via birth right result is optimal either socially or economically.