Taking a loan to keep to your bitcoin accumulation ongoing isn't a bad idea but where you are taking this loan from, the interest rate and the understanding between both parties. You might be expecting your monthly income next week and the market dips, you can take a Ioan from a friend, coworker or from your Boss so that you don't miss the dip in order for you to buy bitcoin at a cheaper price. Such loans might not have interest on them or very little interest that would mean nothing to you.
I will respectfully disagree with you because if you understand what loan is, you will never encourage anyone to take loan to invest in Bitcoin. Even in countries like Japan where interest rate is negative sometimes (that is you payback less than the amount borrowed as government helps you pay) there are several conditions attached to the loan and investing in Bitcoin may not qualify for those conditions. Don't forget that loan have duration to pay back and there is no guarantee that Bitcoin would have given you enough profits to pay back the loan within that duration. Besides, the moment you borrow money to invest in a volatile asset like Bitcoin, you have mortgaged your peace of mind by inviting anxiety into your life, this being what every Bitcoin investor should learn never to do.
It has been abundantly emphasised to only invest what you can afford to leave in Bitcoin for a long term, your money that you don't have urgent need of so borrowing to invest in Bitcoin completely violates this requirements.