So the 2 big things that has the Yonko and Admiral groups shit slinging is Garp tossing Kuzan and BB med diffing Law.
1. Kuzan was tossed outta the air by an obvious top tier with no visible damage so far. BB was bleed outta the air by someone weaker than Garp. If that's an L for Kuzan, it's an even bigger one for BB.
2. Saying Kuzan high diffs or extremes Old Garp or vice versa doesn't really make a good downplay argument when BB had a mid diff against someone below Garp, who is arguably not even low top tier. Doesn't mean BB at least high diffs Garp too?
3. It's always a shame seeing people butcher BB's character for power levels. The guy always avoids fights who those he wants no smoke with, and charges head on at those he truly believes he's stronger than and can take without much issue; He fought Ace and tried to make him join the crew, he fought WB who he thought was dying, he faced Magellan when he had no clue about his powers, he faced WB who he thought was dying, and he attacks Hancock and easily took her out.
4. BB ran way from Akainu saying he wasn't ready, stood down from Old Ray sweating aka didn't wanna fight him(who was losing to Kizaru mind you) and the thought of ambushing Kuzan didn't even cross BB's mind despite literally having the whole squad there. Even when a fight broke out and his crew members frozen, BB still took the passive route which is consistent with his character.