I would imagine being electrocuted, or having a captive bolt driven through your head are stressful too?
Especially if the Captive Bolt or electric leaves the animal conscious and it starts being skinned while still alive?

On the other hand their concerns about welfare may be longer than the animals slaughter. 
Does welfare during the animals entire life in the farm mean anything to you?
If an animal is treated well its entire life in a farm, that animal has had good welfare, if not, it hasn't. 
But some pretend to be concerned about welfare when really they are concerned about brown people living in Canada. 
It is easy to spot those racist idiots. 
People who are concerned with animal welfare a vegetarian or vegan. People whose concerns do not go beyond the second the animal is slaughtered. are concerned about brown people living in Canada.