"... to pick up her best TV supporting actress trophy for 'American Horror Story,' and he got unnecessarily freaked out when she bumped his elbow." That's how it's put in WaPo's "Golden Globes 2016: Leonardo DiCaprio’s Lady Gaga incident and 12 other things you missed" by Stephanie Merry and Emily Yahr.
I've watched that 10 times and I'm quite sure Merry and Yahr are obtuse. Lady Gaga did not just "confidently walk by" DiCaprio. She deliberately but subtly and sexily collided with him because it was funny and fun and she smiled. He could have been irked at perceived disrespect, but he knew he was on camera and performed a jovial 2-part reaction. Watch the eyebrows. Part 1 is not Jack Nicholsonian enough so he does a second, more exaggerated eyebrow raising. It's acting. He wasn't "unnecessarily freaked out," which makes him seem wimpy-jumpy. Unfair.
ADDED: One reason it happened is that DiCaprio is expanding out into the aisle. He's manspreading — the upper-body form of manspreading. Gaga's hips — in that high-structured dress — are flaring out in a way that used to be called "secretary spread" — so: womanspreading. It was a spread fest.