Getting stuck and being unable to progress is one thing. Enough people do SL1 runs that it's obvious this game was designed to be conquered through skill. As in any other RPG ever, grinding is a way to make up for any deficiencies in skill.
So if you're stuck, it's because you lack the skill needed to get through the game at your current power level - the solution is, of course, to muster up the difference in skill or continue fighting weaker foes to boost your power. And of course to grind effectively requires an appropriate measure of lower-level skill. In either of these cases, the game requires that you prove your skill to earn the right to progress.
Respeccing is a very different case. You've already done the work to boost your power - now you're merely deciding that you'd like to try a different approach to using your character. Deciding that "well, the player should be locked into whatever stats they already have" is really just arbitrary. The player being able to adapt his/her solution with the resources (in this case, soul level) he/she has already earned is perfectly appropriate within the "use your skills to progress" formula. There's really no reason to force the player to jump through additional hoops just for the sake of adding friction.
It's not as though respeccing suddenly turns a SL30 character into a SL60 character. The player still has to earn the right to whatever power level he/she has reached - only now the player has more freedom to allocate that power level as he/she sees fit. And it's not an unlimited capability, either - the player still has to manage the respecs by earning whatever item is required to perform it.
I don't see how this disrupts the merit-based progression system that's already in place. It's just another option available to players for advancing through the game.
And to say that this will negatively impact PvP is just laughable. You're either prepared for human opponents, or you're not.