Is it deer resistant?

Yes

Knife Acacia is deer resistant.

Acacia cultriformis

Deer: Rarely
Height: 20 ft (6.1 m)
Spread: 15 ft 1 in (4.6 m)
Zones: 9–11
Light: Full sun

Tree

Knife Acacia (Acacia cultriformis)

Photo: Debate at en.wikipedia · Public domain

Also called Knife-Leaf Wattle, Dogtooth Wattle

More details

Light: Full sun, Partial shade
Water: Low, Medium
Type: Tree
Maintenance: Low
Bloom: Fall, Spring, Summer, Winter

More in Acacia