I believe the main reason why we're in disagreement is because I think that the focus should be aimed at solving problems on the biggest and most secure blockchain in the world (Bitcoin), rather than implementing or trying to implement sidechains so we can incorporate a lot of smaller, let's call them ways to exchange different "tokens". The fact that this is driven by a for profit organization which will actually be touching the Bitcoin codebase and that has centralization on it's agenda concerns me greatly.
Hence I'd rather see us all working in unity to solve the problems we're facing on the main chain, rather than anywhere else.
Why 'biggest'? In my area people struggle mightily to have the biggest tires on their pickup truck. The theory/running joke is that the motivation for this desire is correlated with psychological issues brought on by sub-par genital mass. The problem with giant tires on a pickup truck are many due implementation problems, and the inherent tradeoffs start to make the vehicle be actually useful for almost nothing...except perhaps impressing one's like-minded friends who are typically straight and of the same gender making the effort a costly exercise in frustration.
As for security, a blockchain is a blockchain. It's security is associated with a certain number of factors. The difficulty of subverting it is synonymous with 'security' in my mind. That is associated with the hashing power that went into it, the ability of it to build freely and securely, and the amount of distribution.
Sidechains would promote at least the same amount of Bitcoin blockchain hashing since it would be necessary even if/when it is unprofitable to mine Bitcoin alone. If the Bitcoin blockchain could remain small and tight this would promote distribution which would help mitigate various forms of attack and provide a lot of flexibility in fighting against attacks if/when they do occur.
Please please please understand that those of us who are enthusiastic about sidechains are very much interested in their ability to defend the Bitcoin blockchain and Bitcoin as both a source of monetary value as well as an empowering technology for individuals. Sidechains are completely about Bitcoin in my mind and I think it likely that the same can be said for most of those who share my enthusiasm for the solution.
I do think it's fair to make some progress in pruning in a manner as described in Satoshi's whitepaper (or a better method of achieving the same effect) before simply tweaking the block size (which is a simple setting made at compile time.) If this development (pruning) has been de-prioritized in order to focus on newer and better GUI's then it's time to pay the piper.