This study will be of interest. The summary:

The collaborative study indicated relative toxicity of six artificial sweeteners (aspartame, sucralose, saccharine, neotame, advantame, and acesulfame potassium-k) and 10 sport supplements containing these artificial sweeteners. The bacteria found in the digestive system became toxic when exposed to concentrations of only one mg./ml. of the artificial sweeteners.

Also, see this brief video.

It is heartening to note that erythritol, a no-calorie sweetener, seems safe.

Obviously, it does no harm to avoid artificial sweeteners. No one, so far as I know, maintains that they are required for a healthy diet.