No doubt about it. The question is if it's worth it. Yes there is a risk - but a population that largely accepts risk from unhealthy eating or smoking should IMHO not be all that worried about the in comparison about the (a 2nd IMHO) small increase in risk when using MSE compared to an annoying product. Also, ones own behavior, like how do you handle or react to email attachments, how up-to-date do you keep your system, what websites do you visit (a 3rd IMHO) probably has a larger impact than your choice of anti-virus software.
In addition, if the anti-virus software annoys users enough they soon start ignoring its popups and always just click them away, so that they end up missing actual alerts.
In addition to those, there is also a risk that the 3rd party AV solutions themselves have security holes. I know Google Project Zero has found a few issues that make you question whether you are not opening yourself up to worse attacks by using these products than you would by not using them.
In addition, if the anti-virus software annoys users enough they soon start ignoring its popups and always just click them away, so that they end up missing actual alerts.