Amazon - I don't believe they will scam you. It is one of the most trusted eCommerce companies in the world and I have been a loyal customer of Amazon.com since several years.
I am not really into affiliate marketing but I do use it a little bit. Their operating agreement is pretty tough to follow. For example, they do not allow advertising the affiliate links in Search engines. This means, you cannot advertise your affiliate links directly. However, you can advertise your website and place affiliate links in the advertised website. Also, they do not allow using redirected, intermediate links to products. There is nothing explicitly mentioned about social media or email marketing. However, it is pretty obvious that it is not allowed since they have made certain link placement requirements that will not work with social media and email marketing. Throughout the program policies, they mention "your site" and "placing links on the site", which indirectly requires that you cannot place the links anywhere else, including emails and social media posts.
My wife purchased a few products using my affiliate links and I never got paid for those sales! Well, it's their policy and they seem to be pretty smart about it. According to their policy, we cannot buy products for our friends, relatives and ourselves. I have no complaints about it.
In this case, the complaint itself says he used email marketing and social media promotion. For most people, both of them means nothing but spamming. I do not know about this particular case, but most people who claim email marketing do nothing but send spam emails to thousands of people. Those who claim to be doing social media marketing are doing nothing but posting links in all groups, which is a clear case of spam. Whether you call it SPAM or not, according to Amazon, it is not an allowed practice. You are allowed to use the Amazon affiliate links only in your approved website.
How to deal with this case?
If you receive a notice like this, this is what I suggest you to do:
The money you are talking about is a pretty big amount. So, don't give up on it easily. When they call you, talk to them with confidence. Tell them you are an established blogger who follow ethical business practices. Tell them you are marketing your website through email marketing and social media marketing and also tell them you are a "popular and influential blogger". Try to convince them that you are doing only ethical practices to make affiliate revenue. Also mention you have invested a good amount of money to promote Amazon products, which is a mutually beneficial business. If you can convince Amazon that you followed ethical practices and not spamming/illegal methods, Amazon may decide to release your payment.
Amazon affiliate program is definitely not a scam or fraud program. Such complaints of non-payment of affiliate commissions comes up once in a while and I'm pretty sure this happened due to non-compliance of their terms and conditions.