Its partly class bigotry, partly old wounds from the original split and partly the fact the two codes are in direct competition with each other. We shouldn't expect anything less and if we are failing it is due to our own inaction rather than their action.
Scotland is a great example, our total lack of investment and action is why there is no RL presence in that country, not because every attempt has been thwarted by Scottish RU.
Class consciousness is a factor. In Australia, Australian Rules Football has prospered partly because it has always been seen as open to everybody, from the richest to the poorest, and it has always had a lot of female supporters. I was amazed when I moved to Melbourne to work in the eighties, the crowds at VFL games were very different to the crowds at rugby league games iin Sydney. This has helped the AFL get a foothold in GPS Schools in Sydney, it is seen as a sport with a bit of prestige attached to it. That is one of the things that people pay big money for when they choose an expensive school.
But tradition is the biggest reason that fee paying schools, and the older universities, are rusted on rugby union strongholds.
It is a cop-out to talk about bigotry. It would be far better to look at the real reasons, and learn from them, wherever possible. Somebody who follows his father into a particular school, college, or university and who does so partly because of family traditions is not a bigot.