“Albert got all defensive when I commented on his design.”

At work, a software designer made a design for a new product. You saw some problems with the design, so you talked to him about the problems. He got angry and fought back against each point. Now you're telling another coworker about it. You say:

Albert got all defensive when I commented on his design.

(someone) got all (adjective)

To "get all ___" means to show too much of an emotion: 

There's no need to get all angry about it. I was just trying to help!

She's at an age now where she gets all embarrassed whenever I say anything to her friends or classmates.

These sentences mean the same thing as they would without "all", but "all" helps to show how you feel about the person's emotion. It shows that you think this level of emotion is too much and not needed.

This phrase is just used in casual spoken English.

get defensive (about something)

"Getting defensive" means acting like someone is emotionally attacking you. Here are a few examples of people "getting defensive":

• You are eating dinner at your sister's house, and you put some extra salt on your food. She says, "What, is my cooking not good enough for you?"
• You give some suggestions to your employee about how to organize her e-mail better. She argues back against every point that you make, and seems upset about it.

comment on (something)

To "comment on" a topic means to talk about it and give your opinion on it. Here are some examples:

A news reporter asks a politician:

Senator Fredericks, would you care to comment on President Obama's statement?

A woman can say to her sister:

You didn't even comment on my haircut!