//I feel uncomfortable with the fact that the UK govt can interfere in Scottish laws in general.//
Why? The Scottish government, like all local administrations, only exercises powers that are devolved from the UK government. These powers remain the ultimate responsibility of the national government and can be modified, amended curtailed or withdrawn at any time.
//Way to make the young hate the older generation more!//
Only temporarily, until they become older and no longer know everything.
//…can anyone explain to me what part of the UK's equality laws this scottish law is alleged to contravene?//
Gladly. One such aspect: the UK’s Equality Act allows for the provision of “single sex” spaces (toilets, changing rooms, domestic violence refuges, etc.). Admission to these is segregated on the basis of biological sex, not gender which may have been assumed on a whim. Most people (particularly women) find this quite reasonable; they welcome being able to use these spaces and would not welcome the intrusion into them of men pretending to be women. The Scottish “Gender Recognition Certificates” will not be recognised in the rest of the UK. Holders of them (say, a 16 year old youth who has decided he might like life as a “woman” for a while) will not be admitted and this will lead to conflict (supporters of “Trans Rights” are not renowned for being shrinking violets) and it is wholly unnecessary.
The UK government has a responsibility to the whole of the UK. Not just to the 8% who live in Scotland and certainly not solely to the 0.5% of that small percentage who want to pretend to be something they are not. The devolved powers afforded to the Scottish government are limited and not without boundaries. Those suggesting that Scotland is ruled from Westminster are quite correct.