Trifle with
Definition 1 of 2
Pro Tip 1/3Negative Connotation
Using 'trifle with' suggests negative judgment and criticism towards the behavior. 
Don't trifle with her trust; it's all she has left.
Pro Tip 2/3Serious Matters
It is often used when the matters are serious and important to someone. 
The jury must not trifle with the evidence presented in this case.
Pro Tip 3/3Potential Harm
Implies that not treating something or someone with respect could cause harm. 
One should never trifle with safety procedures at a construction site.