First things first let's get this straight. Bellamy was a great villain in Jaya and people need to understand that just because you hate a character that doesn't mean they're bad.
He was very well written, had a nice design, impactful scenes,one of the best quotes in One Piece, and if he wasn't as great of a heel as he was that one shot wouldn't have had nearly as much impact as it did.
He was anti every thing that One Piece stood for and it was great (Wapols another good villain).
He was almost killed by Doflamingo but was deliberately spared if you go and read that chapter again.
And after suffering both of those embarrassments what did he do
He dusted the dirt off his shoulder and kept it moving opting to better himself and challenge his beliefs rather than throw a pity party and never amount to anything
Yes he continued to stan Doflamingo but I'll address that at the end of this post.
Now your next few points are based around strength which mean diddly squat in relation to the quality of his character but I'll address them anyways.
Yes he lost his block but that's after doing stuff that imo was cool, having some nice dialogue, being completely scratchless for the majority of it, and being put up against an OP barrier ability and still holding strong after slamming into it at spring speed multiple times (imagine running into a brick wall a couple of tines at full speed but you're superhuman and the brick wall is super duper hard) and then getting the upper hand before being hit by the Kings Punch which knocked out a full health Blue Gilly that Luffy said he'd never seen anything like.
And yes he was being pummeled by Dellinger but he was already damaged and couldn't oppose the family if he wanted to remain in Doffy's good graces and was too shocked and too much of a mess to fight back if you take his dialogue in the scene to mean anything.
I'll get to the stanning thing at the end of the post.
Okay onto this.......so can you please tell me why Doflamingo insulting him diminishes his character?
I'll get to that.
Yes he was used as a human shield now what does that have to do with the quality of his character?
Okay so now we're at the meat and potatoes of the post.
Now let me start this off by saying that whenever I read a story or a watch a series I try to put myself in the mindsets of the characters so that in able to get the fill picture and understand why they make the decisions that they do even if those aren't the ones I would make otherwise I may misconstrue stuff or I'd feel too judgemental and doing this with Bellamy has given me a better understanding of not only his but Doflamingo's character.
Now from what we know of Bellamy's young life he was a rich boy who admired Doflamingo and wanted to become a pirate just like him and asked to take up his symbol.
Now we can see the effects that his social status had on Doflamingo from the get go.
He doesn't dislike Bellamy because of his attitude or strength or beliefs as can clearly be seen with Doflamingo's crew but because he gave up what he longed for since he was ejected from heaven "wealth" and the fact that Bellamy simply gave that up to be and I roughly quote "a cut above the people who sit about dreaming of bluer seas"(which means he's a go getter) disgusts him and you can bet that if Bellamy had came with a sob story like Law for Doflamingo shyt would have played out differently.
Rather than write something new for thus next part I'll just copy and paste an old post I made somewhere:
"The way I see it is that he admired Doflamingo and wanted to be like him so when he was given Doflamingo's symbol, was told not to lose, and made the oath to never do sk (and we know how big oaths are in this series) everything after that point in Bellamy's pirating career was for the sake of that symbol, all of his wins, any strength, he gained, his pride, maybe indirectly all amplified by the promise and overtime that got to his head and we ended up with the strength obsessed Bellamy who never lost and thought that he could coast on Doflamingo's symbol but once all that shyt happened to him and he lost his crew the only thing he could hold onto was his old promise which was directly connected to his self worth and representative of his life's work along with his shame that he wanted to recover from.
It would be very easy for Bellamy to switch sides and blame Doflamingo for how how he turned out but instead of Oda making him a very loose Brownbeard 2.0 which would have been the generic route and what most series do he took the unconvetional route (which is one of the reasons I love that scene so much) and has Bellamy admit he's a massive fukk up idiot who took the wrong path in life on his own volition but just because things didn't go as Bellamy imagined they would Bellamy won't act as though he has no fault in this scenario and take the moral high ground/easy route.
He made his bed and he's gonna lie in it regardless of the outcome because switching sides on a whim just because he's at his wits end is the most shameful thing he believes he could do at this point and wants to go out fighting the new man he admires.
It's one if the most samurai like decisions he could make actually.
His dream is gone and now he's a sad husk bouncing around trying to hold onto whatever bit of pride he can.
Now while I don't necessarily agree with all of his rationalizations and decisions I don't need a character to do what I would do or what I think is right as long as it's well written and while Oda definitely could have interrogated him more into this arc his plotline is still compelling for me and it's what I'm most interested in.
Just because you don't like a character that doesn't mean they're bad.
I may not like Bartolomeo but I still can say he's a good character who simply doesn't fit my tastes and consider him just as apart of the plot and shouldn't be glossed over like I do for characters I'm a fan of like Bellamy, Kyros, and Cavendish.