When there's no understanding

I have a major issue developing where I have stopped an activity that has been my husband's interest for many years, and to which I have been expected to contribute, because it was just taking way too much money from our shared funds and I just didn't want to lose any more money at this stage of our lives - both nearly 60.  My husband has always considered this "investment" will fund his retirement but is a high-risk, low return endeavour and very few people actually make money from it.  This has been going on about 15 years and I've had enough as we have lost hundreds of thousands of dollars! 

My husband is of the firm view that I have reneged on a commitment and that we have not seen the "investment" through to the end and that I have done this just to hurt him.  I have more superannuation than he does (5x?) and our only other major asset is our family home and so he is convinced I have done this just to hurt him in retirement.  

How do I make him realise that this is a not a wise, money-making activity and our money can be invested more responsibly?  His ADHD brain gets stimulated by this activity but Blind Freddy can see it's a losing investment?  

It is so frustrating.  When I told him I wanted to have more of a say in how OUR money was spent, he said he didn't care and we needed to see this through.  I think I should have a say in how my money is spent too - surely - after giving it a red hot go for 15 long years?  It's not like I am pulling out after 5 minutes.