When you talk to people with templates and threats, or prejudge that a person is a spammer or some kind of other offender, your behaviour is no better than what you allege this peron to be doing.
Nonsense. For a start, seeing someone spam and concluding that the person is a spammer is not prejudging, it's just judging. You don't like threats? Should we not tell people that what they're doing will get them blocked and just block them without warning? Or perhaps you think blocking them is somehow unfair and we should just accept whatever people do?
Templates are used for convenience. It is much quicker to type {{subst:test}} than a couple of lines explaining why we want them to stop. If you make vandal fighting harder you will reduce the number of vandal fighters which will increase the length of time it takes for vandalism to be found and fixed and increase the amount of vandalism that gets missed completely. Not being very friendly to spammers and vandals is a small price to pay to get vandalism fixed promptly.