This video skips over the major benefit of masks: protecting other people from viruses or bacteria you may be spreading through simple breathing as it expels droplets. Coughing and talking expels many more droplets. Masks short stop this.
Yes, masks are dangerous if you use them the wrong way. Many things are dangerous to the user if used the wrong way. Everyone should learn to use masks the right way and get the most effective mask they can. Only people who are well trained in mask use should enter a sick room environment.......Individual doctors such as this one can give misleading opinions. Mask use is a mainstream medical professional recommendation. His peers do not agree with him in the context of use outside of the sickroom environment