Not that it seems to have anything to do with Single Player Offline being removed but those claiming that Log In authentication is not DRM need to actually go and re-read the current defination of Digital Rights Management which by the way is what D.R.M stands for. You can just go do a google search if you want and shock you'll get the same answers from places other than Wikipedia including the likes of News Papers, the BBC, University's, Computer Groups and even Digital Publishing groups.
D.R.M is considered to include any methods built into an Electrical Product or Service with the aim of controling the use of the product or device after sale, including but not limited to preventing resale or use of the product in a manner different to that which the original developer intended.
Simply by having you forced to LOG IN to the launcher Elite Dangerous has D.R.M, while yes it is a core part of the game if the game was originally published as intended with an OFFLINE component then you wouldn't need to login and thus there would be no D.R.M. How is the Launcher Log In DRM? Because it checks to see if you OWN the game, it authenticates it against the store and if you do not have it on your account then you are unable to login, hence D.R.M.
The reason DRM has such a bad name is because its seen as being a limitation forcing people who have brought a product to use a product the way the author wants them to and only that way. In most cases it does not prevent piracy as can be seen by the near next day cracking of most AAA games even with complex DRM management or heck even the piracy of games that use Steam or other platforms.. To most end users it is seen simply as a company saying we don't care that you've paid for the product you'll use it how we want or not at all and you most certainly will not resell it or anything like that.
In some countries certain aspects of it's use have caused legal challenges the same as EULA's have as most EULA's try and say you only 'loan' the software and do not have the right to resell, however most Countries have laws which allow the reselling of goods that you have purchased and software is considered a 'Good' this is in part why 2nd hand console games are traded and sold. In the few cases where such has gone to court the software companies typically have lost and been forced to allow the user to sell their product, this includes companies such as Adobe, Microsoft and yes even Blizzard (who have tried to prevent players from reselling things like Star Craft 2 accounts, WoW accounts etc).
Despite that aspect of DRM (login checks) Always Online technology started in the market, it's seen as hey look if you have to be online we can CHECK and see if you have the right to be on our product.. and it has not been taken well by the consumer base at all, Microsoft tried it with the X-Box One.. and they faced that large of a backlash that they quickly backpeddled and changed their minds on it and (unsurprisingly) the producer who was unwilling to at first budge suddenly 'retired' days after the backpedal.
Electronic Arts was forced to issue refunds, and eat a lot of humble pie over Sim City, they ended up patching in an offline mode and actually changing the entire way that Origin works allowing the 'Great game' gaurentee.
Blizzard was forced to issue refunds and actually taken to court in a number of countries and had it's South Korean offices raided by the Government over Diablo 3's.
Steam is in court over certain aspects of it's DRM and refund policy.
So yeah DRM is in the game and the removal of Single Player Offline means that DRM free versions of it can no longer be shipped.