When you have other young, talented players hitching their wagons to the team long term, and your one true star-tier player eying the exits as soon as possible, as a fan suddenly you lose that warm fuzzy feeling you might've had about your young core that could turn into a perennial Cup contender for the next decade.
I don't think Dahlin is doing it so maliciously, and I get why he'd want that for his career and livelihood... but we finally have an actually promising team, we haven't even turned the corner yet, after a 12 year drought... and we already have players playing hard ball. Not a great feeling as a fan.