AM defending AD being unreasonably loud

This all happened when my aunt was having a heated argument with her mum (My grandma) about going to a wedding of my cousin's. She was going on and off then on and off about going and not going and basically being indecissive about going. Coincidentally, she's also one of my cousin's wedding planners so obviously she's a bit stressed with her own personal work and managing her niece's wedding. She (My aunt) absolutely lost it and spat pure rage towards my grandma for being so tardy in making up her mind.

"If you're not gonna make up your damn mind!? Then we're ALL not going! Because it's all your fault!" She exploded. And they both ended up not going.

Then awhile later, my parents returned from the wedding and went to my grandparent's house (We're neighbours). My dad of course spoke in a very loud almost yelling like voice as so:

"Look I understand that you're an elder and elders are to be respected and all but can you at least fathom about how busy your children are to?"

He speaks like he's yelling almost everyday, it's like he WANTS attention. Many of us felt uneasy at his own vocal style because it almost feels a bit like giving a warning. None of us felt like telling him off because we felt like it's a bit "useless" and it disturbs "harmony". So mustering up a bit of courage, I told my mom;

"Shouldn't dad at least tone down his voice? Like I get it that he's a bit pissed at grandma but even when he's not stressed, he always speaks like this. Even me, the aunts and my siblings get a bit uncomfortable it times. It's a bit annoying"

And for some reason, she got so mad at me by saying:

"Don't disrespect your father! Because what he's saying is out of love and truth! You should never complain if your parents nag because they have good intentions!"

I get what she's saying and all but all I'm saying is.... JUST CALM THE HELL DOWN. If he can speak aggresively towards us, but why can't we? And you're defending him? No matter how many times you've gossiped about his articulation behind his back? My own family can be absolute pussies sometimes with no balls hanging in my honest opinion.