All new machines are being fucked with - it doesn't matter whether its a Mac of a PC (Linux flavors may also be affected). The reason is in the chips (CPUs).
The CPUs from back in the days of the Pentium 4/Celeron have an operating system on-chip that is invisible to the actual installed OS. From what I remember it is called Minx(?). It allows anyone CPU access to all and any processes without the installed OS being alerted to any fuckery going on.
The power that this back door gave to the operator vastly expanded with the iCore processors of Intel (i3, i5, i7, etc) - wifi connection even when the computer is turned off, remote access any time, file transfer without any knowledge of the user, etc.
As to your Mac - it runs the new Intel iCore (VPro) processors which is why you are having problems.
So what you are experiencing is hidden operator fuckery that has installed software to prevent you from going to the sites that you want to go to.
If you love Macs get the last and fastest version of a PowerPC Mac (laptop or desktop) and then get the Morph OS operating system - it is based on the Amiga OS 4.0 (of 1980s glory) and runs faster than any Mac running today. There is also a repository of over 50,000 free software packages for this combo. PowerPC chips have no back doors and the Morph (And Amiga 4.0) OS system has all the spyware stripped out (Oh, you didn't know? 90% of any operating system is spyware) which is why it runs so fast compared to new systems.
My machine rarely has any problems whatsoever - it is a 2006 Toshiba with a Centrino processor running @ 1.73GHz. It has Windows XP SP3 installed plus Knoppix 8.1, Linux Mint 18.3, and Spinrite 6.0. The browsers I use are (in order of most usage): Maxthon 4.4.8 (the newer ones are fucking HORRIBLE), Opera 36, Firefox 15 with FireFTP, Chromium 49, & I never go above version 10.0.9 on Adobe Flash.
My machine runs better than any 'new' Windows 10 POS (piece of shit) regardless of how new it is.