Apperently, scanning ports on elasticache node that belongs to your account from a VM that belongs to your account is considered as abuse by AWS.

[…] We’ve received a report(s) that your EC2 instance(s) Instance Id: i-xxxxxxxx IP Address: x.x.x.x has been implicated in activity which resembles scanning remote hosts on the internet for security vulnerabilities. Activity of this nature is forbidden in the AWS Acceptable Use Policy (https://aws.amazon.com/aup/). We’ve included the original report below for your review. […]

I think I know now, where the bad hacker movies take their inspiration.
Oh well… I’ll not use nmap. I will stay away from the ping command as well, because I may hack the pentagon.