In some cases, LoCo's (or just new-hire or new-base crew) are used by airline managers as a vehicle to undermine the wage structure, union agreements and T's & C's of existing staff. Not unsurprisingly, this can lead to a degree of tension. The airlines most affected in this way will tend to be the legacy large carriers, as they also tend to have more a more "expensive" workforce. It is not possible to know which group is "right" or "wrong", but it is possible to realise that the fallout from such issues creates massive and fundamental change in the work and domestic lives of existing staff, and change can often be painful: Given this, emotions may run high.
LoCo's are changing the industry for all of us. The customer is the main beneficiary financially. The question remains open as to whether the customer benefits in any other area, or cares about it.