Earlier quoted context omitted.
Trump has continually let Russia do as it pleases, he kowtowed in Syria to Putin, he kowtowed by threatening to constantly defund NATO, he kowtowed in Crimea. The facts are just too obvious. Trump is pro-Russia, he's done nothing but allow it to expand and influence US elections, too.
How is asking for fair proportional funding of european defense something we should be responsible for? I understand we benefit from that too, but why should we carry the burden more than the direct beneficiaries?
In south east asia the argument can be seen differently - but even so, the US protects SK, Japan, Taiwan, and Australia to keep open the South China Sea. If that benefit disappeared the US wouldn't be as vigorous in its defense.
The reason presidents prior kept NATO together was because it is an extremely strong alliance that can protect each other's economic interests. If the US loses NATO now, they are simply no longer hegemon.